Journal articles on the topic 'Heterojunction semiconductor devices'
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WESSELS, B. W. "MAGNETORESISTANCE OF NARROW GAP MAGNETIC SEMICONDUCTOR HETEROJUNCTIONS." SPIN 03, no. 04 (December 2013): 1340011. http://dx.doi.org/10.1142/s2010324713400110.
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Narrow gap III–V semiconductors have been investigated for semiconductor spintronics. By alloying these semiconductors with manganese magnetic semiconductors result. Large magnetoresistance (MR) effects have been observed in narrow gap magnetic semiconductor p–n heterojunctions. The MR which is positive is attributed to spin selective carrier scattering. For an InMnAs / InAs heterojunction a diode MR of 2680% is observed at room temperature and high magnetic fields. This work indicates that highly spin-polarized magnetic semiconductor heterojunctions can be realized that operate at room temperature. Devices based on the MR include spin diodes and bipolar magnetic junction transistors. We utilize the diode MR states to create a binary logic family.
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Sang, Xianhe, Yongfu Wang, Qinglin Wang, Liangrui Zou, Shunhao Ge, Yu Yao, Xueting Wang, Jianchao Fan, and Dandan Sang. "A Review on Optoelectronical Properties of Non-Metal Oxide/Diamond-Based p-n Heterojunction." Molecules 28, no. 3 (January 30, 2023): 1334. http://dx.doi.org/10.3390/molecules28031334.
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Diamond holds promise for optoelectronic devices working in high-frequency, high-power and high-temperature environments, for example in some aspect of nuclear energetics industry processing and aerospace due to its wide bandgap (5.5 eV), ultimate thermal conductivity, high-pressure resistance, high radio frequency and high chemical stability. In the last several years, p-type B-doped diamond (BDD) has been fabricated to heterojunctions with all kinds of non-metal oxide (AlN, GaN, Si and carbon-based semiconductors) to form heterojunctions, which may be widely utilized in various optoelectronic device technology. This article discusses the application of diamond-based heterostructures and mainly writes about optoelectronic device fabrication, optoelectronic performance research, LEDs, photodetectors, and high-electron mobility transistor (HEMT) device applications based on diamond non-metal oxide (AlN, GaN, Si and carbon-based semiconductor) heterojunction. The discussion in this paper will provide a new scheme for the improvement of high-temperature diamond-based optoelectronics.
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Mizuno, Tomohisa, Mitsuo Hasegawa, and Toshiyuki Sameshima. "Novel Source Heterojunction Structures with Relaxed-/Strained-Layers for Quasi-Ballistic CMOS Transistors." Key Engineering Materials 470 (February 2011): 72–78. http://dx.doi.org/10.4028/www.scientific.net/kem.470.72.
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We have studied new abrupt-source-relaxed/strained semiconductor-heterojunction structures for quasi-ballistic complementary-metal-oxide-semiconductor (CMOS) devices, by locally controlling the strain of a single strained semiconductor. Appling O+ ion implantation recoil energy to the strained semiconductor/buried oxide interface, Raman analysis of the strained layers indicates that we have successfully relaxed both strained-Si-on-insulator (SSOI) substrates for n-MOS and SiGe-on-insulator (SGOI) substrates for p-MOS without poly crystallizing the semiconductor layers, by optimizing O+ ion implantation conditions. As a result, it is considered that the source conduction and valence band offsets EC and EV can be realized by the energy difference in the source Si/channel-strained Si and the source-relaxed SiGe/channel-strained SiGe layers, respectively. The device simulator, considering the tunneling effects at the source heterojunction, shows that the transconductance of sub-10 nm source heterojunction MOS transistors (SHOT) continues to increase with increasing EC. Therefore, SHOT structures with the novel source heterojunction are very promising for future quasi-ballistic CMOS devices.
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Gaudillat, Pierre, Jean Moïse Suisse, and Marcel Bouvet. "Humidity Insensitive Conductometric Sensors for Ammonia Sensing." Key Engineering Materials 605 (April 2014): 181–84. http://dx.doi.org/10.4028/www.scientific.net/kem.605.181.
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Interest in molecular materials has been driven in large part by their various and prosperous applications, especially in the domain of organic electronics, where they offer many advantages as well as alternative approaches compared to their inorganic counterparts. Most of conductometric transducers are resistors[[ and transistors[[[, but rarely diodes[6]. In our laboratory, we designed and characterized new molecular material based devices. Molecular Semiconductor Doped Insulator (MSDI) heterojunctions were built around a heterojunction between a Molecular Semiconductor (MS) and a Doped Insulator (DI)[7][8]. This new device exhibits interesting electronic properties that allow ammonia sensing in a large humidity range at room temperature.
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Zhuiykov, Serge, and Zhen Yin Hai. "Surface Functionalization of Two-Dimensional Vertically Aligned Semiconductor Heterojunctions." Key Engineering Materials 765 (March 2018): 8–11. http://dx.doi.org/10.4028/www.scientific.net/kem.765.8.
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Large-scale fabrication of two-dimensional (2D) nanomaterials by vapor phase depostion enabled the establishment of vertically aligned semiconductor herterojunctions. However, the property modulation of 2D semiconductor heterojunctions remains chanlleging within such thin layers. Herein, we proposed a general strategy towards the surface functionlization of 2D semiconductor heterojunctions simply by two-step atomic layer deposition (ALD) process with following post-annealing. TiO2-WO3 heterojunction was taken as a typical case in this work and its electrochemical properties were significantly improved via the proposed strategy. This strategy may open a new pathway for facile functionalization of 2D nanomaterials for the energy conversion and storage devices.
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Mi, Yi Lin. "Spin Diffusion in the Finite Magnetic Heterojunction." Key Engineering Materials 727 (January 2017): 410–14. http://dx.doi.org/10.4028/www.scientific.net/kem.727.410.
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Spin diffusion in the finite magnetic heterojunction was explored considering the spin dependent conductivity. In organic semiconductor spintronic devices, the up-spin and down-spin polarons have different density once spin injection happens from ferromagnetic electrodes into organic semiconductors. The difference results in the spin dependent conductivity. The calculations show that the spin injection efficiency is dependent on the spin dependent conductivity and the size of the layers. The spin dependent conductivity has great influence on the spin injection efficiency in the finite magnetic heterojunction, when the spin polarization of the organic semiconductors is moderate.
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Ni, Junhao, Quangui Fu, Kostya (Ken) Ostrikov, Xiaofeng Gu, Haiyan Nan, and Shaoqing Xiao. "Status and prospects of Ohmic contacts on two-dimensional semiconductors." Nanotechnology 33, no. 6 (November 18, 2021): 062005. http://dx.doi.org/10.1088/1361-6528/ac2fe1.
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Abstract In recent years, two-dimensional materials have received more and more attention in the development of semiconductor devices, and their practical applications in optoelectronic devices have also developed rapidly. However, there are still some factors that limit the performance of two-dimensional semiconductor material devices, and one of the most important is Ohmic contact. Here, we elaborate on a variety of approaches to achieve Ohmic contacts on two-dimensional materials and reveal their physical mechanisms. For the work function mismatch problem, we summarize the comparison of barrier heights between different metals and 2D semiconductors. We also examine different methods to solve the problem of Fermi level pinning. For the novel 2D metal-semiconductor contact methods, we analyse their effects on reducing contact resistance from two different perspectives: homojunction and heterojunction. Finally, the challenges of 2D semiconductors in achieving Ohmic contacts are outlined.
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Yu, Edward T. "Cross-Sectional Scanning Tunneling Microscopy of Semiconductor Heterostructures." MRS Bulletin 22, no. 8 (August 1997): 22–26. http://dx.doi.org/10.1557/s0883769400033765.
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As characteristic dimensions in semiconductor devices continue to shrink and as advanced heterostructure devices increase in prominence, the ability to characterize structure and electronic properties in semiconductor materials and device structures at the atomic to nanometer scales has come to be of outstanding and immediate importance. Phenomena such as atomic-scale roughness of heterojunction interfaces, compositional ordering in semiconductor alloys, discreteness and spatial distribution of dopant atoms, and formation of self-assembled nanoscale structures can exert a profound influence on material properties and device behavior. The relationships between atomic-scale structure, epitaxial growth or processing conditions, and ultimately material properties and device behavior must be understood for realization and effective optimization of a wide range of semiconductor heterostructure and nanoscale devices.Cross-sectional scanning tunneling microscopy (STM) has emerged as a unique and powerful tool in the study of atomic-scale properties in III-V compound semiconductor heterostructures and of nanometer-scale structure and electronic properties in Si micro-electronic devices, offering unique capabilities for characterization that in conjunction with a variety of other, complementary experimental methods are providing new and important insights into material and device properties at the atomic to nanometer scale. In this article, we describe the basic experimental techniques involved in cross-sectional STM and give a few representative applications from our work that illustrate the ability, using cross-sectional STM in conjunction with other experimental techniques, to probe atomic-scale features in the structure of semiconductor heterojunctions and to correlate these features with epitaxial-growth conditions and device behavior.
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Kelly, M. J. "A second decade of semiconductor heterojunction devices." Microelectronics Journal 24, no. 8 (December 1993): 723–39. http://dx.doi.org/10.1016/0026-2692(93)90073-n.
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Rashid, Muhammad Haroon, Ants Koel, and Toomas Rang. "Nano- and Micro-Scale Simulations of Ge/3C-SiC and Ge/4H-SiC NN-Heterojunction Diodes." Materials Science Forum 1004 (July 2020): 490–96. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.490.
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During the last decade, silicon carbide (SiC) and its heterostructures with other semiconductors have gained a significant importance for wide range of electronics applications. These structures are highly suitable for high frequency and high power applications in extremely high temperature environments. SiC exists in more than 200 different polycrystalline forms, called polytypes. Among these 200 types, the most prominent polytypes with exceptional physical and electrical attributes are 3C-SiC, 4H-SiC and 6H-SiC. Heterostructures of these SiC polytypes with other conventional semiconductors (like Si, Ge) can give rise to interesting electronic characteristics. In this article, Germanium (Ge) has been used to make heterostructures with 3C-SiC and 4H-SiC using a novel technique called diffusion welding. Microscale and nanoscale simulations of nn-heterojunction of Ge/3C-SiC and Ge/4H-SiC have been done. Microscale devices have been simulated with a commercially available semiconductor device simulator tool called Silvaco TCAD. Whereas nanoscale devices have been simulated with QuantumWise Atomistix Toolkit (ATK) software package. Current-voltage (IV) curves of all simulated devices have been calculated and compared. In nanoscale device, the effects of defects on IV-characteristics due to non-ideal bonding (lattice misplacement) at heterojunction interface have been analyzed. Our simulation results reveal that the proposed heterostructure devices with diffusion welding of wafers are theoretically possible. These simulations are the preparations of our near future physical experiments targeted to fabricate SiC based heterostructure devices using diffusion bonding technique.
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Gorman, Brian P., Andrew G. Norman, and Yanfa Yan. "Atom Probe Analysis of III–V and Si-Based Semiconductor Photovoltaic Structures." Microscopy and Microanalysis 13, no. 6 (November 14, 2007): 493–502. http://dx.doi.org/10.1017/s1431927607070894.
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The applicability of atom probe to the characterization of photovoltaic devices is presented with special emphasis on high efficiency III–V and low cost ITO/a-Si:H heterojunction cells. Laser pulsed atom probe is shown to enable subnanometer chemical and structural depth profiling of interfaces in III–V heterojunction cells. Hydrogen, oxygen, and phosphorus chemical profiling in 5-nm-thick a-Si heterojunction cells is also illustrated, along with compositional analysis of the ITO/a-Si interface. Detection limits of atom probe tomography useful to semiconductor devices are also discussed. Gaining information about interfacial abruptness, roughness, and dopant profiles will allow for the determination of semiconductor conductivity, junction depletion widths, and ultimately photocurrent collection efficiencies and fill factors.
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Eo, Jung Sun, Jaeho Shin, and Jung Sun Eo. "Artificial Synapse Based on 1D/2D Hybrid Heterostructure." ECS Meeting Abstracts MA2022-01, no. 57 (July 7, 2022): 2365. http://dx.doi.org/10.1149/ma2022-01572365mtgabs.
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Molecular functional devices have been investigated through the study of molecular structure and its corresponding discrete orbital states since it determines the transport behaviors. [1,2] In contrast to the conventional strategy, we have demonstrated a novel strategy and design rule for realizing molecular-scale functions based on the energy band engineering in molecular heterojunction with two-dimensional (2D) semiconductors [3,4]. Recently, we have designed molecular heterojunction selector and the nonlinearity design rule with the role of the molecular dipole moment orientation which controls the band bending of the 2D semiconductor [4]. Likewise, various role of the molecular self-assembled monolayer (SAM) in hybrid heterostructure device with 2D semiconductor can give a novel and diverse functionality to the device that it can be a powerful platform for the next-generation functional devices. We implemented ferrocene substituted alkanethiol SAMs, which is a redox active molecule [5], in 2D MoS2 field-effect transistor (FET) structure. The redox state (oxidation or reduction) of the SAM is controlled through the gate bias and the oxidized molecular states (Fc -> Fc+) can act as a localized gate at the interface between molecule/2D semiconductor (MoS2) which the conductance of the n-type MoS2 channel can be modulated. This MoS2 FET with non-volatile multistate MoS2 channel can be suggested as electrochemically programmed molecular heterojunction artificial synapse. [1] L. A. Bumm, J. J. Arnold, M. T. Cygan, T. D. Dunbar, T. P. Burgin, L. Jones, D. L. Allara, J. M. Tour, P. S. Weiss, Science 271, 1705 ( 1996),. [2] H. Song, Y. Kim, Y. H. Jang, H. Jeong, M. A. Reed, T. Lee, Nature 462, 1039 ( 2009). [3] J. Shin, S. Yang, Y. Jang, J. S. Eo, T.-W. Kim, T. Lee, C.-H. Lee, G. Wang, Nat. Commun. 11, 1 (2020). [4] J. S. Eo, J. Shin, S. Yang, T. Jeon, J. Lee, S. Choi, C.-H. Lee, G. Wang, Adv. Sci. 2101390 (2021). [5] Y. Zhao, S. Bertolazzi, M. S. Maglione, C. Rovira, M. Mas-Torrent, P. Samori, Adv. Mater. 32, 2000740 (2020).
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Gardner, Carl L., and Christian Ringhofer. "The Chapman-Enskog Expansion and the Quantum Hydrodynamic Model for Semiconductor Devices." VLSI Design 10, no. 4 (January 1, 2000): 415–35. http://dx.doi.org/10.1155/2000/91289.
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A “smooth” quantum hydrodynamic (QHD) model for semiconductor devices is derived by a Chapman-Enskog expansion of the Wigner-Boltzmann equation which can handle in a mathematically rigorous way the discontinuities in the classical potential energy which occur at heterojunction barriers in quantum semiconductor devices. A dispersive quantum contribution to the heat flux term in the QHD model is introduced.
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Alesgerovna, Elmira. "İNFLUENCE OF THİN FİLMS ON PHOTOELECTRİC PROPERTİES OF SOLAR CELLS BASED ON p-GaAs/n-Cd0.25Zn0.75S0.8Te0.2 HETEROJUNCTİONS." Grail of Science, no. 18-19 (September 4, 2022): 211–13. http://dx.doi.org/10.36074/grail-of-science.26.08.2022.37.
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In general, heterojunctions, like electronic devices, are non-linear elements, which means that their OCA cannot be described by the usual Ohm's law. When illuminated from the side of the n-type semiconductor, the radiation is absorbed in the p-type semiconductor and creates an electron-hole pair. The short-circuit current and open-circuit voltage are the maximum current and voltage provided by the p-n junction, so the power of the p-n junction at these points is zero.[4,6,7] The FF parameter, called the fill factor, characterizes the maximum power of the p-n heterophotocell and graphically characterizes the squareness of the VAC heterojunction. In VAC, it is determined by the area of the rectangle:
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Wang, Qinglin, Yu Yao, Xianhe Sang, Liangrui Zou, Shunhao Ge, Xueting Wang, Dong Zhang, et al. "Photoluminescence and Electrical Properties of n-Ce-Doped ZnO Nanoleaf/p-Diamond Heterojunction." Nanomaterials 12, no. 21 (October 26, 2022): 3773. http://dx.doi.org/10.3390/nano12213773.
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The n-type Ce:ZnO (NL) grown using a hydrothermal method was deposited on a p-type boron-doped nanoleaf diamond (BDD) film to fabricate an n-Ce:ZnO NL/p-BDD heterojunction. It shows a significant enhancement in photoluminescence (PL) intensity and a more pronounced blue shift of the UV emission peak (from 385 nm to 365 nm) compared with the undoped heterojunction (n-ZnO/p-BDD). The prepared heterojunction devices demonstrate good thermal stability and excellent rectification characteristics at different temperatures. As the temperature increases, the turn-on voltage and ideal factor (n) of the device gradually decrease. The electronic transport behaviors depending on temperature of the heterojunction at different bias voltages are discussed using an equilibrium band diagram and semiconductor theoretical model.
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Houshmand, M., M. H. Zandi, and Nima E. Gorji. "Hybrid Structure for Solar Cells Based on SWCNT/CdS." Nano Hybrids 8 (December 2014): 15–26. http://dx.doi.org/10.4028/www.scientific.net/nh.8.15.
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Recently, we considered the application of carbon nanotubes as the buffer layer between the CdS and Cu (In,Ga)Se2thin film solar cells. In this work the structure of a p-n heterojunction solar cell is analyzed including the single walled carbon nanotubes as the absorber and CdS as n-type semiconductor window layer. The interface and current-voltage characteristics of this proposed structure are studied exerting the general formulation of the p-n heterojunction solar cells proposed by Fonash. We propose that SWCNTs/CdS heterojunction solar cell can overlap with a main part of the sunlight spectrum leading to improve efficiency and short circuit current. The interesting property of such devices is that the light can inter to the device from the absorber as carbon nanotubes are transparent semiconductor nanostructures. The results of this study can be extended to graphene nanolayers as it has been extensively studied by the PV community in recent years.
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Long, Gen, Kenneth Sabalo, Natalie MacDonald, Michael Beattie, and Mostafa Sadoqi. "Photocurrent Enhancement by Introducing Gold Nanoparticles in Nanostructures Based Heterojunction Solar Cell Device." MRS Advances 2, no. 15 (2017): 817–24. http://dx.doi.org/10.1557/adv.2017.146.
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ABSTRACTIn this paper, we report a first hand study of plasmon-enhanced photocurrent observed in hybrid nanostructures based heterojunction solar cell. The heterojunction solar cell was fabricated, using chemically synthesized narrow gap, IV-VI group semiconductor nanoparticles (PbS) of 3∼6nm diameter, wide gap semiconductor ZnO nanowires of 500nm∼1 μm length and ∼50nm diameter, and gold nanoparticles (∼5nm to 30nm), by spin-coating (∼20cycles) onto FTO glasses, in ambient conditions (25°C, 1atm). The synthesized nanostructures were characterized by XRD, UV-VIS absorption, SEM, TEM, solar simulator, etc. Nanostructures of variant sizes were integrated in to the heterojunction devices to study the effects on photocurrent and solar cell performance. The sizes, lengths, thickness of nanostructures were optimized to have best solar cell devices. The effects of fabrication conditions (such as growth temperature, growth time, anneal temperature, ligand treatments, in air or in N2, etc.) on device performance were also studied. The architecture of film stack, i.e., the positions of Au nanoparticles and PbS nanoparticles were also studied. It was confirmed that introducing Au nanopartiles with proper size would lead to the increase of photocurrent. The key challenges were to minimize the trap states and optimize the interface of nanostructures.
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Sánchez-Vergara, María Elena, Raquel Carrera-Téllez, Paulina Smith-Ruiz, Citlalli Rios, and Roberto Salcedo. "The Effect of the Indium(III) Phthalocyanine Chloride Films on the Behavior of Flexible Devices of Flat and Disperse Heterojunction." Coatings 9, no. 10 (October 17, 2019): 673. http://dx.doi.org/10.3390/coatings9100673.
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By means of flat-heterojunction structures based on small semiconductor molecules (MSCs), an analysis of the indium(III) phthalocyanine chloride (In(III)PcCl) film as a constituent of optoelectronic devices was performed. The study included the behavior of In(III)PcCl playing three different roles: a donor species, an electronic acceptor, and a hole layer carrier. The flat-heterojunction structures were prepared by vacuum deposition method that permits a controlled layer-by-layer growth of high purity films. The investigated structures were characterized by scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy and optical bandgaps were obtained by Tauc’s and Cody’s methods. As the structures exhibit a large spectral absorption in the visible range, they were incorporated into flat-heterojunction devices based on flexible and rigid substrates. However, during the synthesis of those structures, the disperse heterojunction arrangement was found and indeed it showed to be more efficient than the initial flat-heterojunction. In order to complement these results, disperse heterojunction arrangement structure as well as its bandgap value were obtained by DFT calculations. Finally, the electronic behavior of both fabricated devices, disperse heterojunction and flat-heterojunction were compared.
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PEARTON, S. J. "ION IMPLANTATION IN III–V SEMICONDUCTOR TECHNOLOGY." International Journal of Modern Physics B 07, no. 28 (December 30, 1993): 4687–761. http://dx.doi.org/10.1142/s0217979293003814.
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A review is given of the applications of ion implantation in III–V compound semiconductor device technology, beginning with the fundamentals of ion stopping in these materials and describing the use of implantation for both doping and isolation. There is increasing interest in the use of MeV implantation to create unique doping profiles or for the isolation of thick device structures such as heterojunction bipolar transistors or multi quantum well lasers, and we give details of these areas and the metal masking layers necessary for selective area processing. Finally, examples are given of the use of implantation in a variety of III–V devices.
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Mendil, Nesrine, Mebarka Daoudi, Zakarya Berkai, and Abderrahmane Belghachi. "Charge Carrier Mobility Behavior in the SubPc/C60 Planar Heterojunction." Zeitschrift für Naturforschung A 73, no. 11 (October 25, 2018): 1047–52. http://dx.doi.org/10.1515/zna-2018-0142.
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AbstractStructural arrangement and construction are the keys to electron/hole motion through organic semiconductor lattices. In this work, we focused on the disorder energy, temperature, and electric field effects on charge carrier mobilities using a Poole–Frenkel mobility model for SubPc/C60 devices. The results agree with those found in the literature. We observed important temperature, applied voltage, and disorder energy dependencies of the current-voltage characteristics and charge carrier mobilities; these characteristics have the Gunn curve form called negative conductivity, which has been reported in amorphous semiconductors.
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Ray, Biswajit, Aditya G. Baradwaj, Mohammad Ryyan Khan, Bryan W. Boudouris, and Muhammad Ashraful Alam. "Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells." Proceedings of the National Academy of Sciences 112, no. 36 (August 19, 2015): 11193–98. http://dx.doi.org/10.1073/pnas.1506699112.
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The bulk heterojunction (BHJ) organic photovoltaic (OPV) architecture has dominated the literature due to its ability to be implemented in devices with relatively high efficiency values. However, a simpler device architecture based on a single organic semiconductor (SS-OPV) offers several advantages: it obviates the need to control the highly system-dependent nanoscale BHJ morphology, and therefore, would allow the use of broader range of organic semiconductors. Unfortunately, the photocurrent in standard SS-OPV devices is typically very low, which generally is attributed to inefficient charge separation of the photogenerated excitons. Here we show that the short-circuit current density from SS-OPV devices can be enhanced significantly (∼100-fold) through the use of inverted device configurations, relative to a standard OPV device architecture. This result suggests that charge generation may not be the performance bottleneck in OPV device operation. Instead, poor charge collection, caused by defect-induced electric field screening, is most likely the primary performance bottleneck in regular-geometry SS-OPV cells. We justify this hypothesis by: (i) detailed numerical simulations, (ii) electrical characterization experiments of functional SS-OPV devices using multiple polymers as active layer materials, and (iii) impedance spectroscopy measurements. Furthermore, we show that the collection-limited photocurrent theory consistently interprets typical characteristics of regular SS-OPV devices. These insights should encourage the design and OPV implementation of high-purity, high-mobility polymers, and other soft materials that have shown promise in organic field-effect transistor applications, but have not performed well in BHJ OPV devices, wherein they adopt less-than-ideal nanostructures when blended with electron-accepting materials.
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Grätzel, Michael. "Dye-Sensitized Solid-State Heterojunction Solar Cells." MRS Bulletin 30, no. 1 (January 2005): 23–27. http://dx.doi.org/10.1557/mrs2005.4.
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AbstractThe dye-sensitized solar cell (DSSC) provides a technically and economically viable alternative concept to present-day p–n junction photovoltaic devices. In contrast to conventional silicon systems, where the semiconductor assumes both the task of light absorption and charge carrier transport, these two functions are separated in DSSCs. The use of sensitizers having a broad absorption band in conjunction with wide-bandgap semiconductor films of mesoporous or nanocrystalline morphology permits harvesting a large fraction of sunlight. There are good prospects that these devices can attain the conversion efficiency of liquid-electrolyte-based dye-sensitized solar cells, which currently stands at 11%. In this article, we present the current state of the field, the realm of our review being restricted to the discussion of organic molecular hole conductors, which have demonstrated the best performance to date.
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Talukdar, Keka, and Anil Shantappa. "Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction." International Journal of Nanoscience 15, no. 05n06 (October 2016): 1660009. http://dx.doi.org/10.1142/s0219581x16600097.
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Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone–Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.
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Sivula, Kevin. "(Invited) Bulk Heterojunction Organic Semiconductor Photoelectrodes and Photocatalysts for Solar-Driven Water Splitting." ECS Meeting Abstracts MA2022-01, no. 36 (July 7, 2022): 1571. http://dx.doi.org/10.1149/ma2022-01361571mtgabs.
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The bulk heterojunction (BHJ) concept, which has been successfully developed for organic semiconductor-based photovoltaic devices, offers a promising route to high-performance and inexpensive photocatalyst nanoparticles for solar hydrogen production. However, the suitability organic semiconductors (OSs) towards robust and high efficiency photocatalytic water splitting remains an open question. Herein, efforts to understand the stability of OS-based BHJ photoelectrodes for both solar driven water reduction [1] and oxidation [2] are discussed. The integration of a BHJ photoanode and photocathode into a bias-free solar-driven water splitting device is also reported. Finally, the important aspects needed for translating these systems into nanoparticle photocatalysts are examined. ______________ References: [1]L. Yao, N. Guijarro, F. Boudoire, Y. Liu, A. Rahmanudin, R. A. Wells, A. Sekar, H.-H. Cho, J.-H. Yum, F. Le Formal, K. Sivula, J. Am. Chem. Soc. 2020, 142, 7795. [2] H.-H. Cho, L. Yao, J.-H. Yum, Y. Liu, F. Boudoire, R. A. Wells, N. Guijarro, A. Sekar, K. Sivula, Nat. Catal. 2021, 4, 431.
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Grimmeiss, Hermann G., and Erich Kasper. "Today’s Mainstream Microelectronics - A Result of Technological, Market and Human Enterprise." Materials Science Forum 608 (December 2008): 1–16. http://dx.doi.org/10.4028/www.scientific.net/msf.608.1.
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Microelectronics is a central area within information technology, which is still one of the most important global technologies. It will be shown that the development of integrated circuits is based on a long and fascinating history, which is unique in modern time. Yet, the fantastic growth in semiconductor electronics is due to a unique combination of basic conceptional advances, the perfection of new materials and the development of new device principles. A brief survey of the development of microelectronics is given by not only focusing on the history of microelectronics but also taking into account materials and market aspects. Since microelectronics is an extremely complex area, a few criteria and reference points for integrated circuits are given. Thereafter, some examples are presented indicating the rapidly changing state-of-the-art. It will be shown that the development of material science within the area of microelectronics is not always driven by scientific curiosity but often by arbitrary and not always obvious preferences. After a short discussion of the performance advantages and disadvantages of germanium, silicon and III-V compound semiconductors, the SiGe heterojunction bipolar transistor is taken as an example for demonstrating a few important differences in the performance of all-silicon devices with regard to silicon-based heterojunction devices in general. In conclusion, the impact of human enterprise and research policy on the development of microelectronics is briefly discussed.
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Chang, Xiao Ying, and Qian Qiong Wu. "Photovoltaic Solar Cells with Metal Oxide Semiconductor Anode and Mutilayer." Applied Mechanics and Materials 209-211 (October 2012): 1758–61. http://dx.doi.org/10.4028/www.scientific.net/amm.209-211.1758.
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Al doped zinc oxide (AZO) as anode for bulk-heterojunction [regioregular of poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61 butyric acid methyl ester (PCBM)] organic solar cells was investigated. We got efficient flexible solar cells with a highly transparent and electrical conductive NiO film as hole-transporting layer (HTL) on optimized AZO substrate. The strcture of this kind of devices is PET/AZO/NiO/P3HT: PCBM /Al. The highest power conversion efficiency (PCE) on glass substrate is 3.15%, and 1.66% on flexible substrate. The physical and electrical properties of AZO thin film were discussed, and the device photovoltaic characteristics were investigated in detail.
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Gnana Prakash, A. P., and N. Pushpa. "Application of Pelletron Accelerator to Study High Total Dose Radiation Effects on Semiconductor Devices." Solid State Phenomena 239 (August 2015): 37–71. http://dx.doi.org/10.4028/www.scientific.net/ssp.239.37.
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Silicon bipolar junction transistors (BJTs), Silicon-germanium heterojunction bipolar transistors (SiGe HBTs) and metal oxide semiconductor (MOS) devices are the key components of BiCMOS integrated circuits. The semiconductor devices need to withstand very high total doses (100’s of Mrad) for reliable operation of electronic circuits for 8-10 years of LHC operation. The study of radiation tolerance of semiconductor devices up to 100 Mrad of total dose takes longer time with conventional 60Co gamma, proton and electron irradiation facilities and the effects due to these radiations are well understood. Hence it is important to study the effects of heavy ion irradiation on various semiconductor devices. The irradiation time decreases with increasing linear energy transfer (LET) of incident radiation and LET increases with atomic number of the impinging ions. But it is essential to understand the mechanism of energy transfer by different heavy ions in semiconductor devices. Therefore, here we give an overview of different heavy ion interactions with Si BJTs, MOSFETs and SiGe HBTs by primarily focusing on the electrical characteristics of these devices before and after ion irradiation. We show that the irradiation time needed to reach very high total dose can be reduced by using Pelletron accelerator facilities instead of conventional irradiation facilities.
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Yusoff, Nurul Huda, Nur Izzah Abd Azes, and Surani Buniran. "Modification of Thin Film Surface Morphology by Thermal Annealing Process to Enhance Organic Photovoltaic Solar Cell Performance." Advanced Materials Research 879 (January 2014): 144–48. http://dx.doi.org/10.4028/www.scientific.net/amr.879.144.
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This paper reports effect of modification thin film surface morphology using thermal annealing process in order to enhance organic photovoltaic solar cell performance. The organic photovoltaic solar cell (OPV) were fabricated using bulk heterojunction structure, consist of p-type semiconductor of polythiophene (PT) derivative and an n-type of fullerene, C-61 derivative. The devices structure can be named as Al/LiF/polymer composite film/PEDOT-PSS/ITO. For comparison, the devices were varies; as cast and annealed at 125°C for half an hour to modify the thin film surface structure. The performances of the devices were studied by observing the current-voltage characteristics of the device in dark at ambient temperature and under standard A.M 1.5 illumination. The light conversion efficiency of the resulting photovoltaic devices increases from 0.04% (as cast) to 2.3% after thermal annealing process. As a result, the annealed organic photovoltaic devices, show enhanced efficiencies compared with as cast device due to the enhancement in transport properties of polymer base photovoltaic device.
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Rahman, Md Wahidur, Chandan Joishi, Nidhin Kurian Kalarickal, Hyunsoo Lee, and Siddharth Rajan. "High-Permittivity Dielectric for High-Performance Wide Bandgap Electronic Devices." ECS Meeting Abstracts MA2022-02, no. 32 (October 9, 2022): 1210. http://dx.doi.org/10.1149/ma2022-02321210mtgabs.
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In this presentation, we will review recent work on the integration of high permittivity dielectrics with wide and and ultra-wide bandgap semiconductor devices to obtain improved high power and high frequency applications. We will first discuss the use of such structures for vertical power devices. The high permittivity dielectrics help to reduce surface fields and therefore prevent tunnel leakage from Schottky barriers [1]. Insertion of high permittivity dielectrics can also enable better field termination in high voltage vertical devices [2]. We will discuss recent results using such high permittivity dielectrics in vertical device structures based on Gallium Oxide, leading to high vertical electric fields up to 5.7 MV/cm being sustained in the structure. We will discuss the application of these high permittivity dielectrics for three-terminal high frequency [3] and high voltage [4,5] wide bandgap transistor applications. In lateral transistors built from wide and ultra-wide bandgap semiconductors, gate breakdown and non-uniform electric fields lead to average device breakdown fields that are significantly lower than material limits. We will show how high permittivity dielectrics inserted between the gate and drain can prevent gate breakdown, and also create much more uniform electric field profiles. An analytical model to explain this will be presented and compared with 2-dimensional device simulations. Finally, we will show experimental results for lateral devices from the high Al-composition AlGaN [6], -Ga2O3[7], and AlGaN/GaN [8] material systems, where in each case, we are able to achieve state-of-art breakdown performance for devices such as lateral Schottky diodes and transistors. For example, we have achieved up to 8.3 MV/cm field in high Al-content AlGaN devices, >5.5 MV/cm in -Ga2O3-based transistors, and >3 MV/cm lateral electric field in AlGaN/GaN HEMTs. The high breakdown fields also enable us to achieve state-of-art switching figures of merit in these devices. The authors acknowledge funding from NNSA ETI Consortium, AFOSR GAME MURI Program (Program Manager Dr. Ali Sayir), AFOSR (Program Manager Dr. Kenneth Goretta) NSF ECCS- and the DARPA DREAM program (Program Manger Dr. YK Chen), managed by ONR (Program Manager Dr. Paul Maki) for support of the work. References [1] Xia, Zhanbo, et al. "Metal/BaTiO3/β-Ga2O3 dielectric heterojunction diode with 5.7 MV/cm breakdown field." Applied Physics Letters 115.25 (2019): 252104. [2] Lee, Hyun-Soo, et al. "High-permittivity dielectric edge termination for vertical high voltage devices." Journal of Computational Electronics 19.4 (2020): 1538-1545. [3] Xia, Zhanbo, et al. "Design of transistors using high-permittivity materials." IEEE Transactions on Electron Devices 66.2 (2019): 896-900. [4] Kalarickal, Nidhin Kurian, et al. "Electrostatic engineering using extreme permittivity materials for ultra-wide bandgap semiconductor transistors." IEEE Transactions on Electron Devices 68.1 (2020): 29-35. [5] Hanawa, Hideyuki, et al. "Numerical Analysis of Breakdown Voltage Enhancement in AlGaN/GaN HEMTs With a High-k Passivation Layer." IEEE Transactions on Electron Devices 61.3 (2014): 769-775. [6] Razzak, Towhidur, et al. "BaTiO3/Al0. 58Ga0. 42N lateral heterojunction diodes with breakdown field exceeding 8 MV/cm." Applied Physics Letters 116.2 (2020): 023507. [7] Kalarickal, Nidhin Kurian, et al. "β-(Al0.18Ga0.82)2O3/Ga2O3 Double Heterojunction Transistor With Average Field of 5.5 MV/cm." IEEE Electron Device Letters 42.6 (2021): 899-902. [8] Rahman, Mohammad Wahidur, et al. "Hybrid BaTiO3/SiNx/AlGaN/GaN lateral Schottky barrier diodes with low turn-on and high breakdown performance." Applied Physics Letters 119.1 (2021): 013504.
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Jones, K. M., F. S. Hasoon, A. B. Swartzlander, M. M. Al-Jassim, T. L. Chu, and S. S. Chu. "The morphology and microstructure of polycrystalline CdTe thin films for solar cell applications." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 1384–85. http://dx.doi.org/10.1017/s0424820100131553.
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Polycrystalline thin films of II-VI semiconductors on foreign polycrystalline (or amorphous) substrates have many applications in optoelectronic devices. In contrast to the extensive studies of the heteroepitaxial growth of compound semiconductors on single-crystal substrates, the nucleation and growth of thin films of II-VI compounds on foreign substrates have received little attention, and the properties of these films are often controlled empirically to optimize device performance. A better understanding of the nucleation, growth, and microstructure will facilitate a better control of the structural and electrical properties of polycrystalline semiconductor films, thereby improving the device characteristics. Cadmium telluride (CdTe) has long been recognized as a promising thin-film photovoltaic material. Under NREL's sponsorship, the University of South Florida has recently developed a record high efficiency (14.6% under global AM1.5 conditions) thin-film CdS/CdTe heterojunction solar cell for potential low-cost photovoltaic applications. The solar cell has the structure:glass (substrate)/SnO2:F/CdS/CdTe/HgTe (contact)The CdS films were grown from an aqueous solution, while the CdTe films were deposited by the closespaced sublimation method.
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Dupuis, R. D. "III-V semiconductor heterojunction devices grown by metalorganic chemical vapor deposition." IEEE Journal of Selected Topics in Quantum Electronics 6, no. 6 (November 2000): 1040–50. http://dx.doi.org/10.1109/2944.902153.
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Vecchi, Pierpaolo, Alberto Piccioni, Irene Carrai, Raffaello Mazzaro, Michele Mazzanti, Vito Cristino, Stefano Caramori, and Luca Pasquini. "Understanding the Carrier Dynamics of Complex Heterojunctions for Water Splitting through Wavelength-Dependent Intensity Modulated Photocurrent Spectroscopy." ECS Meeting Abstracts MA2022-02, no. 48 (October 9, 2022): 1871. http://dx.doi.org/10.1149/ma2022-02481871mtgabs.
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Metal oxide semiconductors are promising materials to be employed as photoanodes in photoelectrochemical (PEC) devices to drive the oxygen evolution reaction (OER) for the conversion of solar energy into chemical fuels. These materials need to efficiently absorb light, have good bulk transport properties to separate the photogenerated charges, and induce fast charge transfer from the electrode inside the solution. To this aim, the best selected materials are usually combined to form efficient heterojunction structures, often with the help of surface catalysts. The understanding of charge carrier dynamics in complex heterojunctions is of the utmost importance for the performance optimization of photoelectrochemical cells and “ operando” techniques are most valuable, because they provide information about the charge separation, bulk transport, charge transfer at each junction, and at the semiconductor-electrolyte interface of the system upon external stimuli, such as illumination, applied bias and chemical environment. In the presence of multiple competing processes and complex interfaces, which are often found in photoelectrodes for water splitting, the construction of an electrical model that describe the carrier dynamics under a light stimulus can be difficult, since the frequency response of the PEC system may depend on several interlaced resistive and capacitive contributions, which are sometimes difficult to separate or to interpret in an unambiguous fashion. The characterization of the relevant kinetic processes occurring at junctions and semiconductor/electrolyte interfaces can be effectively carried out by implementing wavelength-dependent Intensity Modulated Photocurrent Spectroscopy (WD-IMPS). This innovative approach allows to selectively probe different layer of the heterojunction and identify the electron transport properties in the bulk and at the interface. We employed this straightforward technique to study the carrier dynamics of a WO3/BiVO4/CoFe-Prussian blue heterojunction in a conventional three electrode cell for water splitting, and we identified interfacial recombination processes affecting the semiconductor heterojunction, as well as the positive contribution of the inorganic catalyst on the charge separation efficiency of the BiVO4 layer.[1] Herein, the proposed methodology is used to separate and address the role of each active component within complex interfaces coupled with different catalysts and in different electrolytic environments and represents a valuable tool for improving the understanding of dynamic processes relevant to PEC water splitting. References [1] Vecchi, P., Piccioni, A., Mazzaro, R., Mazzanti, M., Cristino, V., Caramori, S. and Pasquini, L. (2022), Charge Separation Efficiency in WO3/BiVO4 Photoanodes with CoFe Prussian Blue Catalyst Studied by Wavelength-Dependent Intensity Modulated Photocurrent Spectroscopy. Sol. RRL. Accepted Author Manuscript. https://doi.org/10.1002/solr.202200108
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Zheng, Li, Xinhong Cheng, Peiyi Ye, Lingyan Shen, Qian Wang, Dongliang Zhang, Zhongjian Wang, Yuehui Yu, and Xinke Yu. "Semiconductor-like nanofilms assembled with AlN and TiN laminations for nearly ideal graphene-based heterojunction devices." Journal of Materials Chemistry C 4, no. 47 (2016): 11067–73. http://dx.doi.org/10.1039/c6tc03514k.
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Gan, Kwang Jow, Zheng Jie Jiang, Cher Shiung Tsai, Din Yuen Chan, Jian Syong Huang, Zhen Kai Kao, and Wen Kuan Yeh. "Design of NDR-Based Oscillators Suitable for the Nano-Based BiCMOS Technique." Applied Mechanics and Materials 328 (June 2013): 669–73. http://dx.doi.org/10.4028/www.scientific.net/amm.328.669.
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We present three oscillator designs using the negative-differential-resistance (NDR) circuit which is composed of several Si-based metal-oxide-semiconductor field-effect transistor (MOS) devices and one SiGe-based heterojunction bipolar transistor (HBT) devices. These oscillator circuits are composed of the NDR circuit, resistor, inductor, and capacitor. The oscillation frequencies are about several GHz based on the HSPICE simulation results. The circuits are designed using a standard 0.18 μm BiCMOS technique. Because our circuits are mainly made of a BiCMOS-NDR circuit that is different from a tradition NDR device made by a resonant tunneling diode with a quantum-well structure, we can utilize the nanobased BiCMOS process to implement these circuits by further improving the parameters.
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Woodall, Jerry. "Electronic properties of semiconductor interfaces." Proceedings, annual meeting, Electron Microscopy Society of America 45 (August 1987): 334–37. http://dx.doi.org/10.1017/s0424820100126470.
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Over the past decade III-V materials have been successfully commercialized for optoelectronic applications requiring LED's lasers and photodetectors. The success of these materials for these applications is based primarily on the use of heterojunction structures formed by epitaxial techniques in a manufacturing environment. More recently, III-V materials, notably GaAs, have been studied in the R&D environment as possible materials for use in high speed devices and circuits including VLSI. Even though the use of epitaxially grown structures has played a significant role in the success of laboratory scale devices and circuits, there are still several technology problems which will need to be solved before affordable manufacturing can be done. Two important challenges facing the commercialization of these materials for this application are metal contacts, and dielectrics for control and passivation. Both of these challenges are rooted in a common problem. Stated simply, the problem is that at nearly all GaAs/metal or dielectric interfaces the Fermi level is pinned near mid-gap.
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Wang, Feifei, Yuehua Dai, Cheng Ding, Bing Yang, Xing Li, and Lin Jin. "Improved rectification characteristics of the GR/Blue P/GR selector by doping: First-principles study." Journal of Applied Physics 132, no. 8 (August 28, 2022): 085702. http://dx.doi.org/10.1063/5.0090885.
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In this paper, a graphene (GR)/monolayer (ML) blue phosphorous (Blue P)/GR selector was studied based on the first-principles theory. Due to different contact edges, four GR–Blue P lateral heterojunctions were constructed, namely, armchair–armchair (A–A), zigzag–armchair (Z–A), armchair–zigzag (A–Z), and zigzag–zigzag (Z–Z). As demonstrated by the binding energy and Mulliken population, we found that the Z–Z heterojunction was relatively stable. Furthermore, a GR/Blue P/GR selector based on the Z–Z heterojunction interface was proposed with a nonlinear (NL) coefficient is 105. However, the drive current of this device was insufficient. A P atom of the resistive layer was separately substituted with four different atoms (Ni, Cu, N, and Cl) to effectively improve selector performance. The energy band structure was half-metallic when doped with Ni or Cu while the others still maintained semiconductor characteristics, and the bandgap was significantly reduced. The Schottky barrier height and width of the interface (GR–Blue P), with Cl as the substituted impurity, were the smallest, leading to a three order of magnitude increase in the NL coefficient. The calculation shows that GR/Blue P/GR devices can be integrated as selectors in Resistive switching Random Access Memory (RRAM) arrays. This work also has a certain guiding significance for manufacturing new types of two-dimensional lateral selector apparatuses.
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Anderson, Travis J., Karl D. Hobart, Luke O. Nyakiti, Virginia D. Wheeler, Rachael L. Myers-Ward, Joshua D. Caldwell, Francisco J. Bezares, et al. "Electrical Characterization of the Graphene-SiC Heterojunction." Materials Science Forum 717-720 (May 2012): 641–44. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.641.
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Graphene, a 2D material, has motivated significant research in the study of its in-plane charge carrier transport in order to understand and exploit its unique physical and electrical properties. The vertical graphene-semiconductor system, however, also presents opportunities for unique devices, yet there have been few attempts to understand the properties of carrier transport through the graphene sheet into an underlying substrate. In this work, we investigate the epitaxial graphene/4H-SiC system, studying both p and n-type SiC substrates with varying doping levels in order to better understand this vertical heterojunction.
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Yu, Hang, Jianlin Zhou, Yuanyuan Hao, and Yao Ni. "Effective performance improvement of organic thin film transistors with multi-layer modifications." European Physical Journal Applied Physics 91, no. 3 (September 2020): 30201. http://dx.doi.org/10.1051/epjap/2020200138.
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Organic thin film transistors (OTFTs) based on dioctylbenzothienobenzothiophene (C8BTBT) and copper (Cu) electrodes were fabricated. For improving the electrical performance of the original devices, the different modifications were attempted to insert in three different positions including semiconductor/electrode interface, semiconductor bulk inside and semiconductor/insulator interface. In detail, 4,4′,4′′-tris[3-methylpheny(phenyl)amino] triphenylamine (m-MTDATA) was applied between C8BTBTand Cu electrodes as hole injection layer (HIL). Moreover, the fluorinated copper phthalo-cyanine (F16CuPc) was inserted in C8BTBT/SiO2 interface to form F16CuPc/C8BTBT heterojunction or C8BTBT bulk to form C8BTBT/F16CuPc/C8BTBT sandwich configuration. Our experiment shows that, the sandwich structured OTFTs have a significant performance enhancement when appropriate thickness modification is chosen, comparing with original C8BTBT devices. Then, even the low work function metal Cu was applied, a normal p-type operate-mode C8BTBT-OTFT with mobility as high as 2.56 cm2/Vs has been fabricated.
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Cheung, Ka, Jerry Yu, and Derek Ho. "Determination of the Optimal Sensing Temperature in Pt/Ta2O5/MoO3 Schottky Contacted Nanobelt Straddling Heterojunction." Sensors 18, no. 11 (November 5, 2018): 3770. http://dx.doi.org/10.3390/s18113770.
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Nanostructured Schottky barrier gas sensors have emerged as novel semiconductor devices with large surface areas and unique electronic characteristics. Although it is widely known that operating these gas sensors requires heating to an optimal temperature for the highest sensitivity, the fundamental mechanism that governs the temperature-dependent sensitivity has yet been well understood. In this work, we present new evidence to support that thermionic field emission (TFE) is the dominant transport mechanism for Schottky contacted nanostructured heterojunction gas sensors at their optimal sensing temperature. Through the fabrication and characterization of Pt/MoO3 Schottky contacts, and Pt/Ta2O5/MoO3 heterojunctions, we found a previously unreported connection between TFE transport and optimal gas sensing temperature. This connection enables the description of Schottky barrier gas sensing performance using transport theory, which is a major step towards systematic engineering of gas sensors with nanostructured high-k oxide layers.
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Hasegawa, Hideki, Hajime Fujikura, and Hiroshi Okada. "Molecular-Beam Epitaxy and Device Applications of III-V Semiconductor Nanowires." MRS Bulletin 24, no. 8 (August 1999): 25–30. http://dx.doi.org/10.1557/s0883769400052866.
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A scaling-down of feature sizes into the nanometer range is a common trend in silicon and compound semiconductor advanced devices. That this trend will continue is clearly evidenced by the fact that the “roadmap” for the Si ultralarge-scale-integration circuit (USLI) industry targets production-level realization of a 70-nm minimum feature size for the year 2010. GaAs- and InP-based heterostructure devices such as high-electron-mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) have made remarkable progress by miniaturization, realizing ultrahigh speeds approaching the THz range with ultralow power consumption. Due to progress in nanofabrication technology, feature sizes of scaled-down transistors are rapidly approaching the Fermi wavelength of electrons in semiconductors, even at the production level. This fact may raise some concerns about the operation of present-day devices based on semiclassical principles.However, the progress of nanofabrication technology has opened up the exciting possibility of constructing novel quantum devices, based directly on quantum mechanics, by utilizing artificial structures such as quantum wells, wires, and dots. In these structures, new physical effects appear, such as the formation of new quantum states in single and coupled quantum structures, artificial miniband formation in superlattices, tunneling and resonant tunneling in single and multiple barriers, propagation of phase-coherent guided electron waves in quantum wires, conductance oscillations in small tunnel junctions due to single-electron tunneling, and so on. We expect that these effects will offer rich functionality in next-generation semiconductor quantum ULSIs based on artificial quantum structures, with feature sizes in the range of one to a few tens of nanometers. Beyond this, molecular-level ULSIs using exotic materials and various chemical and electrochemical processes other than the standard semiconductor ones may appear, butat present, they still seem to be too far in the future for realistic consideration for industrial applications.
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Ahlgren, D. C., S. J. Jeng, D. Nguyen-Ngoc, K. Stein, D. Sunderland, M. Gilbert, J. Malinowski, et al. "Si-Ge heterojunction bipolar technology for high-speed integrated circuits." Canadian Journal of Physics 74, S1 (December 1, 1996): 159–66. http://dx.doi.org/10.1139/p96-851.
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This review discusses the fundamentals of SiGe epitaxial base heterojunction bipolar transistor (HBT) technology that have been developed for use in analog and mixed-signal applications in the 1–20 GHz range. The basic principles of operation of the graded base SiGe HBT are reviewed. These principles are then used to explore the design optimization for analog applications. Device results are presented that illustrate some important trade-offs in device design. A discussion of the use of UHV/CVD for the deposition of the epitaxial base profile is followed by an overview of the integrated process. This process, which has been installed on 200 mm wafers in IBM's Advanced Semiconductor Technology Center in Hopewell Junction, N.Y., also includes a full range of support devices. The process has demonstrated SiGe HBT performance, reliability, and yield in a CMOS fabrication with the addition of only one tool for UHV/CVD deposition of the epi-base and, with minimal additional process steps, can be used to fabricate full BiCMOS designs. This paper concludes with a discussion of high-performance circuits fabricated to date, including ECL ring'oscillators, power amplifiers, low-noise amplifiers, voltage-controlled oscillators, and finally a 12-bit DAC that features nearly 3000 SiGe HBT devices demonstrating medium-scale integration.
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Ma, Lanchao, Shuixing Dai, Xiaowei Zhan, Xinyang Liu, and Yu Li. "Convenient fabrication of conjugated polymer semiconductor nanotubes and their application in organic electronics." Royal Society Open Science 5, no. 8 (August 2018): 180868. http://dx.doi.org/10.1098/rsos.180868.
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Organic heterojunction is indispensable in organic electronic devices, such as organic solar cells, organic light-emitting diodes and so on. Fabrication of core–shell nanostructure provides a feasible and novel way to prepare organic heterojunction, which is beneficial for miniaturization and integration of organic electronic devices. Fabrication of nanotubes which constitute the core–shell structure in large quantity is the key for the realization of application. In this work, a simple and convenient method to prepare nanotubes using conjugated copolymer of perylene diimide and dithienothiophene (P(PDI-DTT)) was demonstrated. The relationship between preparation conditions (solvent atmosphere, solution concentration and pore diameter of templates) and morphology of nanostructure was studied systematically. P(PDI-DTT) nanotubes could be fabricated in regular shape and large quantity by preparing the solution with appropriate concentration and placing anodic aluminium oxide template with nanopore diameter of 200 nm in the solvent atmosphere. The tubular structure was confirmed by scanning electron microscopy. P(PDI-DTT) nanotubes exhibited electron mobility of 0.02 cm 2 V –1 s –1 in field-effect transistors under ambient condition. Light-emitting nanostructures were successfully fabricated by incorporating tetraphenylethylene into polymer nanotubes.
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SCHRODER, DIETER K. "PROGRESS IN SIC MATERIALS/DEVICES AND THEIR COMPETITION." International Journal of High Speed Electronics and Systems 21, no. 01 (March 2012): 1250009. http://dx.doi.org/10.1142/s0129156412500097.
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Power semiconductor devices are important for numerous applications with power conversion being an important one. Wide energy gap semiconductors SiC and GaN have properties that make them attractive for such applications. Among these properties are high thermal conductivity, high breakdown electric field, wide energy gap, low intrinsic carrier concentration, high thermal stability, high saturation velocity and chemical inertness. These lead to low on-resistance, high breakdown voltage, high frequencies, small volume, and small passive inductors and capacitors. These desirable properties are offset by the higher material costs and higher defect densities. Although wide energy gap devices have been in development for many years, only recently have they become available commercially. Their main competition is silicon power devices with breakdown voltages up to 8000 V and very high surge current capacity. However, silicon power devices are approaching their material limits and wide energy gap devices are beginning to have an impact in the power electronics space. SiC has the advantage of substrates with diameters approaching 150 mm and the ability to grow thermal SiO2 . GaN has the heterojunction advantage, but no viable substrate technology. In fact, a large portion of SiC production is used for GaN substrates. GaN material development has also benefited significantly from the development of optical devices, e.g., light-emitting diodes and lasers.
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Prokes, S. M., and Kang L. Wang. "Novel Methods of Nanoscale Wire Formation." MRS Bulletin 24, no. 8 (August 1999): 13–19. http://dx.doi.org/10.1557/s0883769400052842.
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In recent years, tremendous interest has been generated in the fabrication and characterization of nanoscale structures such as quantum dots and wires. For example, there is interest in the electronic, magnetic, mechanical, and chemical properties of materials with reduced dimensions. In the case of nanoscale semiconductors, quantum effects are expected to play an increasingly prominent role in the physics of nanostructures, and a new class of electronic and optoelectronic devices may be possible. In addition to new and interesting physics, the formation and characterization of nanoscale magnetic structures could result in higher-density storage capacity in hard disks and optical-recording media. Likewise, phonon confinement leads to a drastic reduction of thermal conductivity and can be used to improve the performance of thermoelectric devices.In 1980, H. Sakaki predicted theoretically that quantum wires may have applications in high-performance transport devices, due to their sawtoothlike density of states (E1/2), where E is the electron energy. Since then, most quantum wires have been made by fabricating a gratinglike gate on top of a two-dimensional (2D) electron gas contained in a semiconductor heterojunction or in metal-oxide-semiconductor structures. By applying a negative gate voltage to the system, its structure can be changed from a 2D to a one-dimensional (1D) regime, where electron confinement is achieved by an electrostatic confining potential. It was not until recently that “physical” semiconductor quantum wires with the demonstrated 1D confinement by physical boundaries began to be fabricated.
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Rashid, Muhammad Haroon, Ants Koel, and Toomas Rang. "Effects of the Inclusion of Armchair Graphene Nanoribbons on the Electrical Conduction Properties of NN-Heterojunction 4H-6H/SiC Diodes." Materials Science Forum 962 (July 2019): 29–35. http://dx.doi.org/10.4028/www.scientific.net/msf.962.29.
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In recent years, graphene has sparked the interest of researchers due to its promising electrical and physical attributes. These attributes make it highly suitable to develop electronic devices with ultra-high mobility of charge carriers. Meanwhile silicon carbide (SiC), a wide bandgap semiconductor material, is being used for high temperature optoelectronic applications. SiC has more than 250 different crystalline forms, these are called polytypes. Some of these polytypes (such as 4H-SiC, 6H-SiC and 3C-SiC) have exceptional physical and electrical properties. Electronic devices which have SiC and graphene as their constituent materials may combine the outstanding attributes of both materials. This article attempts to simulate electronic devices having SiC and graphene as their constituent materials. For this purpose, simulations of a novel nn-heterojunction 4H-6H/SiC diodes with the inclusion of an armchair nanoribbon layer have been carried out. All of the simulations have been run using QuantumWise Atomistix Toolkit (ATK) software, which is an atomic scale electronic device simulator. The density of the states, charge carrier densities and current-voltage curves of the simulated devices have been computed. The simulation results showed a significant improvement in the electrical conduction properties of nn-heterojunction 4H-6H/SiC diodes after the inclusion of the armchair graphene nanoribbons. These simulations provide the groundwork for our future experiments, which will be targeted on fabricating high mobility diodes and/or field effect transistors.
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Wang, Helong, Guanchen Liu, Chongyang Xu, Fanming Zeng, Xiaoyin Xie, and Sheng Wu. "Surface Passivation Using N-Type Organic Semiconductor by One-Step Method in Two-Dimensional Perovskite Solar Cells." Crystals 11, no. 8 (August 12, 2021): 933. http://dx.doi.org/10.3390/cryst11080933.
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Surface passivation, which has been intensively studied recently, is essential for the perovskite solar cells (PSCs), due to the intrinsic defects in perovskite crystal. A series of chemical or physical methods have been published for passivating the defects of perovskites, which effectively suppressed the charge recombination and enhanced the photovoltaic performance. In this study, the n-type semiconductor of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is dissolved in chlorobenzene (CB) for the surface passivation during the spin-coating process for depositing the two-dimensional (2D) perovskite film. This approach simplifies the fabrication process of 2D PSCs and benefits the film quality. As a result, the defects of perovskite film are effectively passivated by this method. A better perovskite/PCBM heterojunction is generated, exhibiting an increased film coverage and improved film morphology of PCBM. It is found that this technology results in an improved electron transporting performance as well as suppressed charge recombination for electron transport layer. As a result, PSCs based on the one-step formed perovskite/PCBM heterojunctions exhibit the optimized power conversion efficiency of 15.69% which is about 37% higher than that of regular perovskite devices. The device environmental stability is also enhanced due to the quality improved electron transport layer.
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Ikenoue, Takumi, Satoshi Yoneya, Masao Miyake, and Tetsuji Hirato. "Epitaxial Growth and Bandgap Control of Ni1-xMgxO Thin Film Grown by Mist Chemical Vapor Deposition Method." MRS Advances 5, no. 31-32 (2020): 1705–12. http://dx.doi.org/10.1557/adv.2020.219.
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ABSTRACTWide-bandgap oxide semiconductors have received significant attention as they can produce devices with high output and breakdown voltage. p-Type conductivity control is essential to realize bipolar devices. Therefore, as a rare wide-bandgap p-type oxide semiconductor, NiO (3.7 eV) has garnered considerable attention. In view of the heterojunction device with Ga2O3 (4.5–5.0 eV), a p-type material with a large bandgap is desired. Herein, we report the growth of a Ni1-xMgxO thin film, which has a larger bandgap than NiO, on α-Al2O3 (0001) substrates that was developed using the mist chemical vapor deposition method. The Ni1-xMgxO thin films epitaxially grown on α-Al2O3 substrates showed crystallographic orientation relationships identical to those of NiO thin films. The Mg composition of Ni1-xMgxO was easily controlled by the Mg concentration of the precursor solution. The Ni1-xMgxO thin film with a higher Mg composition had a larger bandgap, and the bandgap reached 3.9 eV with a Ni1-xMgxO thin film with x = 0.28. In contrast to an undoped Ni1-xMgxO thin film showing insulating properties, the Li-doped Ni1-xMgxO thin film had resistivities of 101–105 Ω∙cm depending on the Li precursor concentration, suggesting that Li effectively acts as an acceptor.
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SARGENT, EDWARD (TED) H., and J. M. (JIMMY) XU. "LATERAL INJECTION LASERS." International Journal of High Speed Electronics and Systems 09, no. 04 (December 1998): 941–78. http://dx.doi.org/10.1142/s0129156498000397.
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Since its invention in the 60's, the semiconductor laser has relied on vertical injection of electrons and holes in order to pump the active region to inversion. While many aspects of semiconductor laser development have seen tremendous innovation and marked progress, this vertical injection scheme has remained unchanged. In contrast, the electronic transistor has evolved from the early dominance of vertical injection to today's largely lateral injection CMOS platform, which yielded new performance, functionality, and integrability and enabled the astonishingly successful integrated circuit revolution. The lateral current injection laser offers advantages which go far beyond optoelectronic integrability: it enables new functionalities, post-fabrication processing and engineering, and in some aspects of normal operation it can lead to greatly improved performances. To realize its full potential, this new class of semiconductor lasers deserves the same attention and the intensive iterations of efforts in theory, design, fabrication, and experimental probing as its vertical cousin has been received. We introduce a first-principles, combined theoretical-experimental approach to the exploration of the LCI laser. It reveals the role of lateral ambipolar drift-diffusion of carriers in either hindering or, potentially, in enhancing the provision of gain to the desired optical mode; of two-dimensional bandstructure engineering of the injection path and active region to achieve low differential resistance and efficient modal gain provision; of selective formation and lateral positioning of heterojunction in enabling high-efficiency device operation; and of adiabatic injection of electrons and holes across diffusively-graded heterojunctions in facilitating carrier capture into 2D quantum well states. Our results point to the tremendous promise of lasers based on lateral injection of current in enabling vertical cavity lasers with vastly increased performance and functional diversity; multi-terminal devices such as lasers with capacitive gain and wave-length tunability; high-speed directly-modulated lasers with reduced chirp; and functional devices with directly integrated high-speed longitudinal modulation.
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Nozaki, Tomohiro, Yi Ding, and Ryan Gresback. "Plasma Synthesis of Silicon Nanocrystals: Application to Organic/Inorganic Photovoltaics through Solution Processing." Materials Science Forum 783-786 (May 2014): 2002–4. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.2002.
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Silicon nanocrystals (SiNCs) have unique optical and electronic properties that are advantageous for semiconductor device applications and here their application to solar cell is presented. Free-standing, narrow size distribution SiNCs were synthesized by non-thermal plasma using silicon tetrachloride (SiCl4) successfully. Blended solution of as-produced SiNCs and P3HT, or Poly(3-hexylthiophene-2,5-diyl), was spin-casted to form bulk heterojunction solar cell devices. As the weight fraction of SiNCs increased up to 50 wt%, the short circuit current and the power conversion efficiency dramatically increased, while the open circuit voltage and the fill factor do not change significantly. The improved performance is attributable to increased probability of exciton dissociation at acceptor SiNCs and donor P3HT interface.
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Janipour, Mohsen, I. Burc Misirlioglu, and Kursat Sendur. "A Theoretical Treatment of THz Resonances in Semiconductor GaAs p–n Junctions." Materials 12, no. 15 (July 29, 2019): 2412. http://dx.doi.org/10.3390/ma12152412.
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Semiconductor heterostructures are suitable for the design and fabrication of terahertz (THz) plasmonic devices, due to their matching carrier densities. The classical dispersion relations in the current literature are derived for metal plasmonic materials, such as gold and silver, for which a homogeneous dielectric function is valid. Penetration of the electric fields into semiconductors induces locally varying charge densities and a spatially varying dielectric function is expected. While such an occurrence renders tunable THz plasmonics a possibility, it is crucial to understand the conditions under which propagating resonant conditions for the carriers occur, upon incidence of an electromagnetic radiation. In this manuscript, we derive a dispersion relation for a p–n heterojunction and apply the methodology to a GaAs p–n junction, a material of interest for optoelectronic devices. Considering symmetrically doped p- and n-type regions with equal width, the effect of certain parameters (such as doping and voltage bias) on the dispersion curve of the p–n heterojunction were investigated. Keeping in sight the different effective masses and mobilities of the carriers, we were able to obtain the conditions that yield identical dielectric functions for the p- and n-regions. Our results indicated that the p–n GaAs system can sustain propagating resonances and can be used as a layered plasmonic waveguide. The conditions under which this is feasible fall in the frequency region between the transverse optical phonon resonance of GaAs and the traditional cut-off frequency of the diode waveguide. In addition, our results indicated when the excitation was slightly above the phonon resonance frequency, the plasmon propagation attained low-loss characteristics. We also showed that the existence or nonexistence of the depletion zone between the p- and n- interfaces allowed certain plasmon modes to propagate, while others decayed rapidly, pointing out the possibility for a design of selective filters.