Artykuły w czasopismach: „III-NITRIDE DEVICE”

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Jamal-Eddine, Zane, Yuewei Zhang i Siddharth Rajan. "Recent Progress in III-Nitride Tunnel Junction-Based Optoelectronics". International Journal of High Speed Electronics and Systems 28, nr 01n02 (marzec 2019): 1940012. http://dx.doi.org/10.1142/s0129156419400123.

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Tunnel junctions have garnered much interest from the III-Nitride optoelectronic research community within recent years. Tunnel junctions have seen applications in several material systems with relatively narrow bandgaps as compared to the III-Nitrides. Although they were initially dismissed as ineffective for commercial device applications due to high voltage penalty and on resistance owed to the wide bandgap nature of the III-Nitride material systems, recent development in the field has warranted further study of such tunnel junction enabled devices. They are of particular interest for applications in III-Nitride optoelectronic devices in which they can be used to enable novel device designs which could potentially address some of the most challenging physical obstacles presented with this unique material system. In this work we review the recent progress made on the study of III-Nitride tunnel junction-based optoelectronic devices and the challenges which are still faced in the field of study today.

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Muthuraj, Vineeta R., Caroline E. Reilly, Thomas Mates, Shuji Nakamura, Steven P. DenBaars i Stacia Keller. "Properties of high to ultrahigh Si-doped GaN grown at 550 °C by flow modulated metalorganic chemical vapor deposition". Applied Physics Letters 122, nr 14 (3.04.2023): 142103. http://dx.doi.org/10.1063/5.0142941.

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The heterogeneous integration of III-nitride materials with other semiconductor systems for electronic devices is attractive because it combines the excellent electrical properties of the III-nitrides with other device platforms. Pursuing integration through metalorganic chemical vapor deposition (MOCVD) is desirable because of the scalability of the technique, but the high temperatures required for the MOCVD growth of III-nitrides (>1000 °C) are incompatible with direct heteroepitaxy on some semiconductor systems and fabricated wafers. Thus, the MOCVD growth temperature of III-nitride films must be lowered to combine them with other systems. In this work, 16 nm-thick Si:GaN films were grown by MOCVD at 550 °C using a flow modulation epitaxy scheme. By optimizing the disilane flow conditions, electron concentrations up to 5.9 × 1019 cm−3 were achieved, resulting in sheet resistances as low as 1070 Ω/□. Film mobilities ranged from 34 to 119 cm2 V−1 s−1. These results are promising for III-nitride integration and expand device design and process options for III-nitride-based electronic devices.

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Hangleiter, Andreas. "III–V Nitrides: A New Age for Optoelectronics". MRS Bulletin 28, nr 5 (maj 2003): 350–53. http://dx.doi.org/10.1557/mrs2003.99.

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AbstractWith the advent of bright-blue light-emitting diodes in 1994, violet laser diodes in 1996, and vertical-cavity surface-emitting lasers at telecommunications wavelengths in 2000, all based on nitride-containing III–V compounds, a new age for optoelectronics began. Despite their technological success, III-nitride materials still hold some mysteries. Compared with conventional III–V semiconductors, even commercial nitride devices are of poor material quality. Due to their heteroepitaxial origin, their crystals are full of dislocations. Electrical properties, particularly in the case of p-type material, are fairly unsatisfactory. Still, light-emitting diodes with extremely high brightness and lasers with high power and good lifetime can be produced with III–V nitride compounds. In this review, we will give an overview of the essential properties of nitride materials for optoelectronic devices, their current development status, open questions, and recent device achievements.

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Baten, Md Zunaid, Shamiul Alam, Bejoy Sikder i Ahmedullah Aziz. "III-Nitride Light-Emitting Devices". Photonics 8, nr 10 (7.10.2021): 430. http://dx.doi.org/10.3390/photonics8100430.

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III-nitride light-emitting devices have been subjects of intense research for the last several decades owing to the versatility of their applications for fundamental research, as well as their widespread commercial utilization. Nitride light-emitters in the form of light-emitting diodes (LEDs) and lasers have made remarkable progress in recent years, especially in the form of blue LEDs and lasers. However, to further extend the scope of these devices, both below and above the blue emission region of the electromagnetic spectrum, and also to expand their range of practical applications, a number of issues and challenges related to the growth of materials, device design, and fabrication need to be overcome. This review provides a detailed overview of nitride-based LEDs and lasers, starting from their early days of development to the present state-of-the-art light-emitting devices. Besides delineating the scientific and engineering milestones achieved in the path towards the development of the highly matured blue LEDs and lasers, this review provides a sketch of the prevailing challenges associated with the development of long-wavelength, as well as ultraviolet nitride LEDs and lasers. In addition to these, recent progress and future challenges related to the development of next-generation nitride emitters, which include exciton-polariton lasers, spin-LEDs and lasers, and nanostructured emitters based on nanowires and quantum dots, have also been elucidated in this review. The review concludes by touching on the more recent topic of hexagonal boron nitride-based light-emitting devices, which have already shown significant promise as deep ultraviolet and single-photon emitters.

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Fu, Wai Yuen, i Hoi Wai Choi. "Progress and prospects of III-nitride optoelectronic devices adopting lift-off processes". Journal of Applied Physics 132, nr 6 (14.08.2022): 060903. http://dx.doi.org/10.1063/5.0089750.

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Lift-off processes have been developed as the enabling technology to free the epitaxial III-nitride thin film from a conventional growth substrate such as sapphire and silicon in order to realize a variety of novel device designs and structures not otherwise possible. An epitaxial lift-off (ELO) process can be adopted to transfer the entire film to an arbitrary foreign substrate to achieve various functions, including enhancement of device performance, improvement of thermal management, and to enable flexibility among others. On the other hand, partial ELO techniques, whereby only a portion of the thin-film is detached from the substrate, can be employed to realize unconventional device structures or geometries, such as apertured, pivoted, and flexible devices, which may be exploited for various photonic structures or optical cavities. This paper reviews the development of different lift-off strategies and processes for III-nitride materials and devices, followed by a perspective on the future directions of this technology.

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Zolper, J. C., i R. J. Shul. "Implantation and Dry Etching of Group-III-Nitride Semiconductors". MRS Bulletin 22, nr 2 (luty 1997): 36–43. http://dx.doi.org/10.1557/s0883769400032553.

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The recent advances in the material quality of the group-III-nitride semiconductors (GaN, A1N, and InN) have led to the demonstration of high-brightness light-emitting diodes, blue laser diodes, and high-frequency transistors, much of which is documented in this issue of MRS Bulletin. While further improvements in the material properties can be expected to enhance device operation, further device advances will also require improved processing technology. In this article, we review developments in two critical processing technologies for photonic and electronic devices: ion implantation and plasma etching. Ion implantation is a technology whereby impurity atoms are introduced into the semiconductor with precise control of concentration and profile. It is widely used in mature semiconductor materials systems such as silicon or gallium arsenide for selective area doping or isolation. Plasma etching is employed to define device features in the semiconductor material with controlled profiles and etch depths. Plasma etching is particularly necessary in the III-nitride materials systems due to the lack of suitable wet-etch chemistries, as will be discussed later.Figure 1 shows a laser-diode structure (after Nakamura) where plasma etching is required to form the laser facets that ideally should be vertical with smooth surfaces. The first III-nitride-based laser diode was fabricated using reactive ion etching (RIE) to form the laser facets but suffered from rough mirror facet surfaces that contributed to scattering loss and a high lasing threshold. This is a prime example of how improved material quality alone will not yield optimum device performance.

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Fu, Houqiang. "(Invited) III-Oxide/III-Nitride Heterostructures for Power Electronics and Optoelectronics Applications". ECS Meeting Abstracts MA2022-02, nr 34 (9.10.2022): 1243. http://dx.doi.org/10.1149/ma2022-02341243mtgabs.

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Due to their large bandgap, high critical electric field, and availability of high-quality large-size melt-grown bulk substrates, III-oxides including Ga2O3, Al2O3, In2O3, and their alloys have been extensively investigated for a myriad of electronic and optoelectronic applications. Recently, β-Ga2O3 based power electronics, RF transistors, and ultraviolet (UV) photodetectors have been demonstrated with promising performance. However, p-type β-Ga2O3 is still elusive due to high dopant activation energy (>1 eV), large hole effective mass, and hole trapping. This significantly limits the design freedom for β-Ga2O3 devices. Other p-type semiconductors have been proposed to form heterostructures with β-Ga2O3 such as p-NiO, p-Cu2O, and p-type III-nitrides. As popular wide bandgap semiconductors, III-nitrides are promising candidates to form III-oxide/III-nitride heterostructures to enable advanced device structures and new functionalities. Furthermore, III-oxides and III-nitrides can be epitaxially grown on each other with small lattice mismatch (< 5% for GaN and β-Ga2O3) by the industrial standard epitaxial method MOCVD. For example, vertical GaN violet LEDs grown on n-type β-Ga2O3 substrates have been reported. This talk will present our recent work on III-oxide/III-nitride heterostructures in power electronics and optoelectronics. For power electronics, β-Ga2O3/GaN p-n heterojunctions will first be discussed. The heterojunction via mechanical exfoliation shows decent forward rectifying behaviors and thermal stability up to 200 °C but relatively low breakdown voltages (BV). To improve the breakdown capability, we carried out a comprehensive TCAD simulation study to design mesa edge termination for kV-class β-Ga2O3/GaN p-n heterojunctions. It was found that the electric field crowding effect is the main reason for the low BV. Several mesa edge termination structures were investigated such as deeply-etched mesa, step mesa, and p-GaN guard ring. Second, normally-off AlN/β-Ga2O3 field-effect transistors using polarization-induced doping will be discussed. A large two-dimensional electron gas is formed at the AlN/β-Ga2O3 interface due to polarization effects, and p-GaN gate is used to realize tunable positive threshold voltage. The device transfer and output characteristics with different device structures are also studied. For optoelectronics applications, self-powered spectrally distinctive Ga2O3/GaN heterojunction UV photodetectors grown by MOCVD will be discussed. Opposite current polarities are observed under different illumination wavelengths due to different carrier transports, which can be utilized to distinguish different spectra. These results indicate that (ultra)wide bandgap III-oxide/III-nitride heterostructures are a promising platform to enable new device structures and functionalities.

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Zhang, Shuai, Bingcheng Zhu, Zheng Shi, Jialei Yuan, Yuan Jiang, Xiangfei Shen, Wei Cai, Yongchao Yang i Yongjin Wang. "Spatial signal correlation from an III-nitride synaptic device". Superlattices and Microstructures 110 (październik 2017): 296–304. http://dx.doi.org/10.1016/j.spmi.2017.08.028.

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Gaevski, Mikhail, Jianyu Deng, Grigory Simin i Remis Gaska. "500 °C operation of AlGaN/GaN and AlInN/GaN Integrated Circuits". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2014, HITEC (1.01.2014): 000084–89. http://dx.doi.org/10.4071/hitec-tp16.

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High-temperature technology platform has been developed utilizing planar III-nitride heterostructures approach. The record high electron concentration and mobility in 2DEG channel of III-nitride devices result in very high operation speed and are remarkably stable within a broad temperature range, allowing device operation above 500 °C. The developed IC technology is based on three key elements: (1) exceptional quality III-nitride heterostructure with very high carrier concentration and mobility that enables IC fast operation in a broad temperature range; (2) heterostructure field effect transistor approach that provides fully planar IC structure which is easy to scale and to combine with the other high temperature electronic components; (3) robust design with self-compensating 2DEG load resistors, advance metallization and high-k passivation/gate dielectrics, specially developed for high temperature operation. The feasibility of technology was demonstrated by modeling, design and fabrication of inverter and differential amplifier type of ICs using III-nitride heterostructures. IC's performance was studied using probe station with heating chuck in ambient atmosphere. Temperature stability of structures with various barrier compositions was compared. At temperature exceeding 500 °C the developed ICs show the leakage currents below 10−7A, unit-gain bandwidth above 1 MHz and internal response time 45 ns.

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Islam, Md Sherajul, Md Arafat Hossain, Sakib Mohammed Muhtadi i Ashraful G. Bhuiyan. "Transport Properties of Insulated Gate AlInN/InN Heterojunction Field Effect Transistor". Advanced Materials Research 403-408 (listopad 2011): 64–69. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.64.

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As a promising candidate for future high speed devices InN-based heterojunction field effect transistor (HFET) has gained a lot of attention in recent years. However, InN-based devices are still a less studied compared with other III-nitride based devices. This work investigates theoretically, the electron transport properties of insulated gate AlInN/InN Heterojunction Field Effect Transistor. A self-consistent charge control model based on one-dimensional Schrodinger-Poisson equations is developed. The transport properties of the device are calculated using an ensemble Monte Carlo simulation. The device model incorporates an analytical 3-valley band structure with non-parabolicity for all nitride materials. The scattering mechanisms considered are dislocations scattering, impurity scattering, interface roughness, alloy disorder scattering and phonon scattering. The model also takes into account the highly dominant spontaneous and piezoelectric polarization effects to predict the 2DEG sheet charge density more accurately at the heterointerface. The results obtained are agreed well with the literature.

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Joglekar, Sameer, Mohamed Azize i Tomás Palacios. "Reactive sputtering of III-N materials for applications in electronic devices". MRS Advances 1, nr 2 (2016): 141–46. http://dx.doi.org/10.1557/adv.2016.38.

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ABSTRACTGallium Nitride (GaN) and other III-N semiconductors are rapidly gaining importance in high power and high frequency electronic applications. III-N material based devices are fabricated on heterostructures that are usually grown by high vacuum techniques such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). However, in many applications, it is necessary to regrow thin cap layers of III-N materials during device fabrication. One such application is regrowth of ohmic contacts to III-N devices. Heavily doped n+ GaN, or InGaN grown by MBE or MOCVD is used to obtain low resistance non-alloyed ohmic contacts to GaN based devices. However, from a commercial point of view, this becomes difficult because of the high cost and lack of availability of ultra high vacuum (∼1x10-10 Torr) techniques in most clean room facilities. Reactive sputtering provides a cheaper and more ubiquitous alternative for the growth of thin cap layers on parent MOCVD III-N heterostructures during device fabrication. In this work, we explore the possibility of using reactive sputtering as a method to grow III-N materials as ohmic contacts to GaN based devices.

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Khan, Asif, i Krishnan Balakrishnan. "Present Status of Deep UV Nitride Light Emitters". Materials Science Forum 590 (sierpień 2008): 141–74. http://dx.doi.org/10.4028/www.scientific.net/msf.590.141.

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Ultraviolet light emitting diodes with emission wavelengths less than 400 nm have been developed using the AlInGaN material system. Rapid progress in material growth, device fabrication and packaging enabled demonstration of deep-UV light-emitting devices with emission from 400 to 210 nm with varying efficiencies. For high aluminum alloy compositions needed for the shorter wavelength devices, these materials border between having material properties like conventional semiconductors and insulators, adding a degree of complexity to developing efficient light emitting devices. This chapter provides a review of III-nitride based UV light emitting devices including technical developments that allow for emission in the ultraviolet spectrum, and an overview of their applications in optoelectronic systems.

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Johnson, M. A. L., Zhonghai Yu, J. D. Brown, F. A. Koeck, N. A. El-Masry, H. S. Kong, J. A. Edmond, J. W. Cook i J. F. Schetzina. "A Critical Comparison Between MOVPE and MBE Growth of III-V Nitride Semiconductor Materials for Opto-Electronic Device Applications". MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 594–99. http://dx.doi.org/10.1557/s1092578300003100.

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A systematic study of the growth and doping of GaN, AlGaN, and InGaN by both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy (MOVPE) has been performed. Critical differences between the resulting epitaxy are observed in the p-type doping using magnesium as the acceptor species. MBE growth, using rf-plasma sources to generate the active nitrogen species for growth, has been used for III-Nitride compounds doped either n-type with silicon or p-type with magnesium. Blue and violet light emitting diode (LED) test structures were fabricated. These vertical devices required a relatively high forward current and exhibited high leakage currents. This behavior was attributed to parallel shorting mechanisms along the dislocations in MBE grown layers. For comparison, similar devices were fabricated using a single wafer vertical flow MOVPE reactor and ammonia as the active nitrogen species. MOVPE grown blue LEDs exhibited excellent forward device characteristics and a high reverse breakdown voltage. We feel that the excess hydrogen, which is present on the GaN surface due to the dissociation of ammonia in MOVPE, acts to passivate the dislocations and eliminate parallel shorting for vertical device structures. These findings support the widespread acceptance of MOVPE, rather than MBE, as the epitaxial growth technique of choice for III-V nitride materials used in vertical transport bipolar devices for optoelectronic applications.

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Funato, Mitsuru, i Yoichi Kawakami. "Semipolar III Nitride Semiconductors: Crystal Growth, Device Fabrication, and Optical Anisotropy". MRS Bulletin 34, nr 5 (maj 2009): 334–40. http://dx.doi.org/10.1557/mrs2009.96.

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AbstractSemipolar InGaN/GaN quantum wells (QWs) are quite attractive as visible light emitters. One of the reasons is that a better optical transition probability is expected because of weaker internal electric fields, compared to conventional polar QWs. In addition, in-plane optical polarization anisotropy, which is absent in conventional QWs, is another relevant property because it affects device design and also may provide a means for novel applications. We revealed that the in-plane optical anisotropy in semipolar QWs switched from one direction perpendicular to the [0001] crystal axis to the perpendicular direction as the In composition increases. This is a property unique to semipolar QWs and enables, for example, to make cavity mirrors of laser diodes by cleavage. In this article, we describe the concept of semipolar planes and fabrication of high-quality epitaxial films for semipolar QWs. Furthermore, we discuss device fabrication and optical polarization anisotropy.

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Zavada, J. M. "Revisiting Impurity Doping of III-Nitride Materials for Photonic Device Applications". ECS Transactions 50, nr 6 (15.03.2013): 253–59. http://dx.doi.org/10.1149/05006.0253ecst.

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Brunner, F., J.-T. Zettler i M. Weyers. "Advanced in-situ control for III-nitride RF power device epitaxy". Semiconductor Science and Technology 33, nr 4 (26.03.2018): 045014. http://dx.doi.org/10.1088/1361-6641/aab410.

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Rienzi, Vincent, Jordan Smith, Norleakvisoth Lim, Hsun-Ming Chang, Philip Chan, Matthew S. Wong, Michael J. Gordon, Steven P. DenBaars i Shuji Nakamura. "Demonstration of III-Nitride Red LEDs on Si Substrates via Strain-Relaxed Template by InGaN Decomposition Layer". Crystals 12, nr 8 (15.08.2022): 1144. http://dx.doi.org/10.3390/cryst12081144.

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A III-nitride red LED with an active region temperature of 835 °C on a Si substrate utilizing a strain-relaxed template (SRT) is demonstrated. The peak wavelength blueshifts from 670 nm at 1 A/cm2 to 636 nm at 150 A/cm2. The on-wafer external quantum efficiency was 0.021% at 7 A/cm2 with an emission wavelength of 655 nm. The LED grown on a Si substrate exhibited a 116 nm redshift when compared to a co-loaded LED grown on sapphire. This is attributed to the difference in strain state for the III-nitride layers grown on Si compared to sapphire, allowing for more indium to be incorporated in the LED grown on Si. This suggests efficient III-nitride red LEDs and µLEDs on Si with a SRT can be realized with further material, device structure, and processing optimizations.

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Hite, Jennifer K. "A Review of Homoepitaxy of III-Nitride Semiconductors by Metal Organic Chemical Vapor Deposition and the Effects on Vertical Devices". Crystals 13, nr 3 (24.02.2023): 387. http://dx.doi.org/10.3390/cryst13030387.

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This paper reviews some of the basic issues in homoepitaxial growth of III-nitrides to enable a vertical device technology. It focuses on the use of metal organic chemical vapor deposition (MOCVD) to grow GaN and explores the effects of the native substrate characteristics on material quality, interface composition, and device performance. A review of theoretical work understanding dopants in the ultra-wide III-nitride semiconductors, AlN and BN, is also included for future efforts expanding the technology into those materials.

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Liu, Zhiyuan, Yi Lu i Xiaohang Li. "53‐1: Invited Paper: Enhanced Performance of III‐Nitride‐Based Light‐Emitting Diodes Through Novel Band Engineering and Fabrication Technology". SID Symposium Digest of Technical Papers 54, nr 1 (czerwiec 2023): 761–62. http://dx.doi.org/10.1002/sdtp.16672.

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III‐Nitride‐based light‐emitting diodes (LEDs) are expected to be used in enormous and broad applications. In this paper, our novel band engineering and fabrication technologies are reviewed and discussed for pursuing higher device performance.

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Khediri, Abdelkrim, Abbasia Talbi, Abdelatif Jaouad, Hassan Maher i Ali Soltani. "Impact of III-Nitride/Si Interface Preconditioning on Breakdown Voltage in GaN-on-Silicon HEMT". Micromachines 12, nr 11 (21.10.2021): 1284. http://dx.doi.org/10.3390/mi12111284.

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In this paper, an AIGaN/GaN metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT) device is realized. The device shows normal ON characteristics with a maximum current of 570 mA/mm at a gate-to-source voltage of 3 V, an on-state resistance of 7.3 Ω·mm and breakdown voltage of 500 V. The device has been modeled using numerical simulations to reproduce output and transfer characteristics. We identify, via experimental results and TCAD simulations, the main physical mechanisms responsible for the premature breakdown. The contribution of the AlN/Silicon substrate interface to the premature off-state breakdown is pointed out. Vertical leakage in lateral GaN devices significantly contributes to the off-state breakdown at high blocking voltages. The parasitic current path leads to premature breakdown before the appearance of avalanche or dielectric breakdown. A comparative study between a MOS-HEMT GaN on a silicon substrate with and without a SiNx interlayer at the AlN/Silicon substrate interface is presented here. We show that it is possible to increase the breakdown voltages of the fabricated transistors on a silicon substrate using SiNx interlayer.

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Fernández, Susana, Fernando B. Naranjo, Miguel Ángel Sánchez-García i Enrique Calleja. "III-Nitrides Resonant Cavity Photodetector Devices". Materials 13, nr 19 (5.10.2020): 4428. http://dx.doi.org/10.3390/ma13194428.

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III-nitride resonant cavity-enhanced Schottky barrier photodetectors were fabricated on 2 µm thick GaN templates by radio frequency plasma-assisted molecular beam epitaxy. The optical cavity was formed by a bottom distributed Bragg reflector based on 10 periods of Al0.3Ga0.7N/GaN, an Au-based Schottky contact as top mirror, and an active zone of 40 nm-thick GaN layer. The devices were fabricated with planar geometry. To evaluate the main benefits allowed by the optical cavity, conventional Schottky photodetectors were also processed. The results revealed a planar spectral response for the conventional photodetector, unlike the resonant devices that showed two raised peaks at 330 and 358 nm with responsivities of 0.34 and 0.39 mA/W, respectively. Both values were 80 times higher than the planar response of the conventional device. These results demonstrate the strong effect of the optical cavity to achieve the desired wavelength selectivity and to enhance the optical field thanks to the light resonance into the optical cavity. The research of such a combination of nitride-based Bragg mirror and thin active layer is the kernel of the present paper.

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Chen, Qi, Yue Yin, Fang Ren, Meng Liang, Xiaoyan Yi i Zhiqiang Liu. "Van der Waals Epitaxy of III-Nitrides and Its Applications". Materials 13, nr 17 (31.08.2020): 3835. http://dx.doi.org/10.3390/ma13173835.

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III-nitride semiconductors have wide bandgap and high carrier mobility, making them suitable candidates for light-emitting diodes (LEDs), laser diodes (LDs), high electron mobility transistors (HEMTs) and other optoelectronics. Compared with conventional epitaxy technique, van der Waals epitaxy (vdWE) has been proven to be a useful route to relax the requirements of lattice mismatch and thermal mismatch between the nitride epilayers and the substrates. By using vdWE, the stress in the epilayer can be sufficiently relaxed, and the epilayer can be easily exfoliated and transferred, which provides opportunities for novel device design and fabrication. In this paper, we review and discuss the important progress on the researches of nitrides vdWE. The potential applications of nitride vdWE are also prospected.

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Kang, Jian-Bin, Qian Li i Mo Li. "Effects of material structure on device efficiency of III-nitride intersubband photodetectors". Acta Physica Sinica 68, nr 22 (2019): 228501. http://dx.doi.org/10.7498/aps.68.20190722.

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Purnamaningsih, Retno Wigajatri, Nyi Raden Poespawati i Elhadj Dogheche. "III-Nitride Semiconductors based Optical Power Splitter Device Design for underwater Application". International Journal of Electrical and Computer Engineering (IJECE) 8, nr 5 (1.10.2018): 3866. http://dx.doi.org/10.11591/ijece.v8i5.pp3866-3874.

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In this paper, we introduce III-nitrides based 1× 4 optical power splitter for underwater optical communication applications. To the best of our knowledge, this is a first study for the design of multimode interference (MMI) and four-branch taper waveguide based on GaN/sapphire. The microstructure of GaN semiconductor grown by Metalorganic Chemical Vapor Deposition (MOCVD) on (0001) sapphire reported. The numerical experimental is conducted using the 3D FD-BPM method. The results showed that the optical power splitter has an excess loss of 0.013 dB and imbalance of 0.17 dB. The results open the opportunity for the future device using this technology for the underwater application.

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Bhouri, A., A. Ben Fredj, J. L. Lazzari i M. Said. "Band offset calculations applied to III–V nitride quantum well device engineering". Superlattices and Microstructures 36, nr 4-6 (październik 2004): 799–806. http://dx.doi.org/10.1016/j.spmi.2004.09.036.

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Zhao, Chao, Nasir Alfaraj, Ram Chandra Subedi, Jian Wei Liang, Abdullah A. Alatawi, Abdullah A. Alhamoud, Mohamed Ebaid, Mohd Sharizal Alias, Tien Khee Ng i Boon S. Ooi. "III-nitride nanowires on unconventional substrates: From materials to optoelectronic device applications". Progress in Quantum Electronics 61 (wrzesień 2018): 1–31. http://dx.doi.org/10.1016/j.pquantelec.2018.07.001.

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Jena, Debdeep, John Simon, Albert Kejia Wang, Yu Cao, Kevin Goodman, Jai Verma, Satyaki Ganguly i in. "Polarization-engineering in group III-nitride heterostructures: New opportunities for device design". physica status solidi (a) 208, nr 7 (8.06.2011): 1511–16. http://dx.doi.org/10.1002/pssa.201001189.

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Masui, Hisashi, i Shuji Nakamura. "Nonpolar and Semipolar Orientations: Material Growth and Properties". Materials Science Forum 590 (sierpień 2008): 211–32. http://dx.doi.org/10.4028/www.scientific.net/msf.590.211.

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Nitride-based optoelectronic devices prepared in the c orientation have been successfully introduced to the global marketplace and are changing the way we think about lighting. A part of the research interest has shifted toward nonpolar and semipolar orientations, which has the potential to broaden the scope and impact of this technology. This is because quantum-well structures prepared in nonpolar and semipolar orientations are able to suppress the quantum-confinement Stark effect, which has a negative impact on optoelectronic device performance. The lower crystal symmetry of such orientations provides spontaneously polarized light emission. Despite these attractive properties of nonpolar and semipolar orientations, the corresponding materials growth is not trivial. The present chapter discusses our efforts on growth of III-nitride materials in nonpolar and semipolar orientations and the related material properties.

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Wong, Matthew S., Philip Chan, Norleakvisoth Lim, Haojun Zhang, Ryan C. White, James S. Speck, Steven P. Denbaars i Shuji Nakamura. "Low Forward Voltage III-Nitride Red Micro-Light-Emitting Diodes on a Strain Relaxed Template with an InGaN Decomposition Layer". Crystals 12, nr 5 (19.05.2022): 721. http://dx.doi.org/10.3390/cryst12050721.

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In this study, III-nitride red micro-light-emitting diodes (µLEDs) with ultralow forward voltage are demonstrated on a strain relaxed template. The forward voltage ranges between 2.00 V and 2.05 V at 20 A/cm2 for device dimensions from 5 × 5 to 100 × 100 µm2. The µLEDs emit at 692 nm at 5 A/cm2 and 637 nm at 100 A/cm2, corresponding to a blueshift of 55 nm due to the screening of the internal electric field in the quantum wells. The maximum external quantum efficiency and wall-plug efficiency of µLEDs are 0.31% and 0.21%, respectively. This suggests that efficient III-nitride red µLEDs can be realized with further material optimizations.

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Hagar, B. G., M. Abdelhamid, E. L. Routh, P. C. Colter i S. M. Bedair. "Ohmic co-doped GaN/InGaN tunneling diode grown by MOCVD". Applied Physics Letters 121, nr 5 (1.08.2022): 052104. http://dx.doi.org/10.1063/5.0103152.

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Tunnel junctions (TJs) have recently been proposed as a solution for several III-nitride current problems and to enhance new structures. Reported III-nitride TJs grown by metalorganic chemical vapor deposition (MOCVD) resulted in backward diodes with rectifying behavior in forward bias, even with Mg and Si doping in 1020 cm−3. This behavior limits applications in several device structures. We report a TJ structure based on p+In0.15Ga0.85N/n+In0.05Ga0.95N, where the n-side of the junction is co-doped with Si and Mg and with electron and hole concentrations in the mid-1019 cm−3 for both the n and p dopants. Co-doping creates deep levels within the bandgap that enhances tunneling under forward biased conditions. The TJ structure was investigated on both GaN substrates and InGaN templates to study the impact of strain on the TJ I–V characteristics. The resulting TJ I–V and resistivities reported indicate the potential for this TJ approach in several device structures based on III-nitrides. We are not aware of any previous MOCVD grown TJs that show Ohmic performance in both forward and reverse biases.

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Mudiyanselage, Dinusha Herath, Dawei Wang, Yuji Zhao i Houqiang Fu. "Intersubband transitions in nonpolar and semipolar III-nitrides: Materials, devices, and applications". Journal of Applied Physics 131, nr 21 (7.06.2022): 210901. http://dx.doi.org/10.1063/5.0088021.

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In the last two decades, the third-generation wide bandgap semiconductor III-nitrides have revolutionized a myriad of electronic and photonic devices and applications, including power electronics, extreme-environment electronics, RF amplifiers, and optoelectronics such as light-emitting diodes and laser diodes. Recently, III-nitride heterostructures (e.g., AlGaN/GaN) based intersubband transition (ISBT) has garnered considerable research interest for infrared (IR), terahertz (THz), and ultrafast optoelectronics (e.g., photodetectors and quantum cascade lasers) due to its large conduction band offset, large optical phonon energy, and promising room-temperature operation. This paper presents a comprehensive review on the recent progress and challenges of III-nitrides based ISBT from the perspectives of materials, structures, devices, and applications, with a focus on nonpolar and semipolar III-nitrides. Various device structures have been demonstrated for III-nitrides based ISBT, including quantum wells, dots, and wires, among which AlGaN/GaN quantum wells are the most widely used. The effects of device parameters, crystal orientations, and doping on the ISBT properties of AlGaN/GaN quantum wells are discussed. Although the room-temperature operation is still elusive, theoretical and experimental studies show that nonpolar and semipolar III-nitrides based ISBT exhibits tunable ISBT wavelength from far-IR to THz spectral range with higher efficiency compared with polar c-plane ISBT. This review can serve as a gateway to and an important reference for the recent progress and challenges of III-nitrides based ISBT and its potential applications in sensing, communication, ultrafast optoelectronics, and integrated photonics.

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Brown, J. M., F. A. Baiocchi, D. S. Williams, R. C. Beairsto, R. V. Knoell i S. P. Murarka. "Rutherford backscattering & TEM studies of nitrogen, oxygen & argon incorporation in sputter-deposited titanium nitride films". Proceedings, annual meeting, Electron Microscopy Society of America 45 (sierpień 1987): 250–51. http://dx.doi.org/10.1017/s0424820100126159.

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Titanium nitride films are incorporated into semiconductor device fabrication to form both contacts and diffusion barriers. These films are often deposited by means of reactive sputtering of a titanium nitride target in an argon atmosphere. During the course of the deposition process, gaseous components may be incorporated into the films resulting in changes in their physical and electrical properties.The stress and resistivity of titanium nitride films have been measured as a function of several processing variables: i) target power, ii) substrate bias, iii) pressure and iv) N2/Ar ratio. The concentration of oxygen, nitrogen and argon and their distribution throughout the films were measured using Rutherford Backscattering Spectroscopy of 2.12MeV helium ions generated in a General Ionex 1.7MV accelerator.

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KOMIRENKO, S. M., K. W. KIM, V. A. KOCHELAP i M. A. STROSCIO. "HIGH-FIELD ELECTRON TRANSPORT CONTROLLED BY OPTICAL PHONON EMISSION IN NITRIDES". International Journal of High Speed Electronics and Systems 12, nr 04 (grudzień 2002): 1057–81. http://dx.doi.org/10.1142/s0129156402001927.

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We have investigated the problem of electron runaway at strong electric fields in polar semiconductors focusing on the nanoscale nitride-based heterostructures. A transport model which takes into account the main features of electrons injected in short devices under high electric fields is developed. The electron distribution as a function of the electron momenta and coordinate is analyzed. We have determined the critical field for the runaway regime and investigated this regime in detail. The electron velocity distribution over the device is studied at different fields. We have applied the model to the group-III nitrides: InN, GaN and AlN. For these materials, the basic parameters and characteristics of the high-field electron transport are obtained. We have found that the transport in the nitrides is always dissipative. However, in the runaway regime, energies and velocities of electrons increase with distance which results in average velocities higher than the peak velocity in bulk-like samples. We demonstrated that the runaway electrons are characterized by the extreme distribution function with the population inversion. A three-terminal heterostructure where the runaway effect can be detected and measured is proposed. We also have considered briefly different nitride-based small-feature-size devices where this effect can have an impact on the device performance.

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Weisbuch, Claude, Shuji Nakamura, Yuh-Renn Wu i James S. Speck. "Disorder effects in nitride semiconductors: impact on fundamental and device properties". Nanophotonics 10, nr 1 (18.11.2020): 3–21. http://dx.doi.org/10.1515/nanoph-2020-0590.

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AbstractSemiconductor structures used for fundamental or device applications most often incorporate alloy materials. In “usual” or “common” III–V alloys, based on the InGaAsP or InGaAlAs material systems, the effects of compositional disorder on the electronic properties can be treated in a perturbative approach. This is not the case in the more recent nitride-based GaInAlN alloys, where the potential changes associated with the various atoms induce strong localization effects, which cannot be described perturbatively. Since the early studies of these materials and devices, disorder effects have indeed been identified to play a major role in their properties. Although many studies have been performed on the structural characterization of materials, on intrinsic electronic localization properties, and on the impact of disorder on device operation, there are still many open questions on all these topics. Taking disorder into account also leads to unmanageable problems in simulations. As a prerequisite to address material and device simulations, a critical examination of experiments must be considered to ensure that one measures intrinsic parameters as these materials are difficult to grow with low defect densities. A specific property of nitride semiconductors that can obscure intrinsic properties is the strong spontaneous and piezoelectric fields. We outline in this review the remaining challenges faced when attempting to fully describe nitride-based material systems, taking the examples of LEDs. The objectives of a better understanding of disorder phenomena are to explain the hidden phenomena often forcing one to use ad hoc parameters, or additional poorly defined concepts, to make simulations agree with experiments. Finally, we describe a novel simulation tool based on a mathematical breakthrough to solve the Schrödinger equation in disordered potentials that facilitates 3D simulations that include alloy disorder.

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35

Pavlidis, Spyridon, Dolar Khachariya, Dennis Szymanski, Pramod Reddy, Erhard Kohn, Zlatko Sitar i Ramon Collazo. "(Invited, Digital Presentation) Exploring Interfaces and Polarity to Realize Vertical III-Nitride Superjunction Devices". ECS Meeting Abstracts MA2022-01, nr 31 (7.07.2022): 1313. http://dx.doi.org/10.1149/ma2022-01311313mtgabs.

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In recent years, there has been a surge of research and commercial interest in gallium nitride (GaN)-based devices for power conversion applications. This is largely motivated by the wide bandgap of GaN, which offers a unipolar limit of performance that is larger than that of silicon and silicon carbide. This performance ceiling, however, can be surpassed with the use of superjunction (SJ) structures, a strategy that has now been experimentally proven in both vertical Si- and SiC-based technologies. The ability to selectively dope lateral regions of a semiconductor is a requirement for SJ fabrication, with typical schemes relying on ion implantation, epitaxial regrowth or a combination of both. However, due to the challenges associated with applying conventional selective area doping techniques to GaN, vertical GaN SJ structures have remained elusive. Recently, our team proposed the use of lateral polar junctions (LPJs) to form vertical GaN SJ devices. This approach exploits the natural doping asymmetry between the N-polar and Ga-polar crystal orientations to simultaneously grow N-polar GaN for the n-type pillars and Ga-polar GaN for the p-type pillars. The first part of this talk will present a design framework for GaN SJ devices. This will reveal several critical design requirements: 1) doping in N-polar GaN must be reduced below 5 × 1017 cm-3 to achieve kV-class devices, 2) charge must be tightly balanced between neighboring pillars in the SJ structure to obtain efficient performance and 3) the barrier height to the N-polar GaN region must be tuned to suppress leakage currents and avoid bipolar operation. The next part of the talk will focus on the characterization of rectifying contacts to N-polar GaN. While the analysis of Schottky barrier diodes proved the ability to reduce doping to relevant levels, the low barrier height and enhanced chemical sensitivity of N-polar GaN make it challenging to process adequate devices. Thus, low-pressure chemical vapor deposited (LPCVD) silicon nitride (SiN) interlayers were introduced to increase the barrier height. This approach is enabled by surface-termination dependent barrier height and an amphoteric miniband for enhanced conduction via the interlayer. Moreover, the use of the LPCVD SiN interlayer enables operation of the diodes up to 400 °C compared to less than 200 °C for the reference case. In addition, N-polar GaN camel diodes were also designed, fabricated and tested to better tune the barrier height. The latter structure was incorporated into the first charge-balanced GaN superjunction device. A detailed electrical analysis of the GaN LPJ device will represent the final portion of this talk. The successful demonstration of these experimental building blocks paves the way for the GaN LPJ to be used in future high-voltage GaN SJ devices.

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Mozharov, A. M., A. A. Vasiliev, A. D. Bolshakov, G. A. Sapunov, V. V. Fedorov, G. E. Cirlin i I. S. Mukhin. "Core-shell III-nitride nanowire heterostructure: negative differential resistance and device application potential". Физика и техника полупроводников 52, nr 4 (2018): 475. http://dx.doi.org/10.21883/ftp.2018.04.45824.13.

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AbstractIn this work we have studied volt-ampere characteristics of single core-shell GaN/InGaN/GaN nanowire. It was experimentally shown that negative differential resistance effect can be obtained in the studied heterostructure. On the base of numerical calculation results the model describing negative differential resistance phenomenon was proposed. We assume this effect to be related with strong localization of current flow inside the nanowire and emergence of Gunn effect in this area.

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Mozharov, A. M., A. A. Vasiliev, A. D. Bolshakov, G. A. Sapunov, V. V. Fedorov, G. E. Cirlin i I. S. Mukhin. "Core-Shell III-Nitride Nanowire Heterostructure: Negative Differential Resistance and Device Application Potential". Semiconductors 52, nr 4 (kwiecień 2018): 489–92. http://dx.doi.org/10.1134/s1063782618040231.

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Annab, N., T. Baghdadli, S. Mamoun i A. E. Merad. "Numerical simulation of highly photovoltaic efficiency of InGaN based solar cells with ZnO as window layer". Journal of Ovonic Research 19, nr 4 (sierpień 2023): 421–31. http://dx.doi.org/10.15251/jor.2023.194.421.

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InxGa1-xN, as one promising nitride semiconductor alloys for modern optoelectronic devices, has received extensive attention in recent years. However, due to its powerful modulation of energy band gap from UV to visible spectra (0.7-3.4 eV) and its interesting absorption coefficient can range from 103 to 105 cm-1 , depending on the material properties, it can be considered as a potential candidate for high efficiency solar cells. The actual efficiency reached is (30.38%) [1]. In order to enhance more the efficiency, we perform in this work, a device modeling and numerical simulation using SCAPS software. We optimize the photovoltaic characteristics of a solar cell based on InxGa1-xN. This cell is mainly composed of indium gallium nitride semiconductors for both buffer and active layer p-InxGa1-xN/i-InxGa1-xN and the window layer contains of n-ZnO. The optimization of the various optoelectronic parameters allows improving performance of the solar cell, in addition to absorbing as much solar radiation as possible. The main photovoltaic parameters of the analog device: open circuit voltage, short circuit current density, fill factor and conversion efficiency (η) were compared and analyzed. We have reached the conversion efficiency of 26.11% for a thickness of 1450 nm and an n-doping of 3×1018 cm-3 in the active layer (In0.3Ga0.7N). This study investigates the great potential of InGaN solar cells and can be used for the design and manufacture of high efficiency III-nitride based solar cells.

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Meneghesso, Gaudenzio, Matteo Meneghini, Augusto Tazzoli, Nicolo' Ronchi, Antonio Stocco, Alessandro Chini i Enrico Zanoni. "Reliability issues of Gallium Nitride High Electron Mobility Transistors". International Journal of Microwave and Wireless Technologies 2, nr 1 (luty 2010): 39–50. http://dx.doi.org/10.1017/s1759078710000097.

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In the present paper we review the most recent degradation modes and mechanisms recently observed in AlGaN/GaN (Aluminum Gallium Nitride/Gallium Nitride). High Electron-Mobility Transistors (HEMTs), as resulting from a detailed accelerated testing campaign, based on reverse bias tests and DC accelerated life tests at various temperatures. Despite the large efforts spent in the last few years, and the progress in mean time to failure values, reliability of GaN HEMTs, and millimeter microwave integrated circuits still represent a relevant issue for the market penetration of these devices. The role of temperature in promoting GaN HEMT failure is controversial, and the accelerating degradation factors are largely unknown. The present paper proposes a methodology for the analysis of failure modes and mechanisms of GaN HEMTs, based on (i) DC and RF stress tests accompanied by an (ii) extensive characterization of traps using deep level transient spectroscopy and pulsed measurements, (iii) detailed analysis of electrical characteristics, and (iv) comparison with two-dimensional device simulations. Results of failure analysis using various microscopy and spectroscopy techniques are presented and failure mechanisms observed at the high electric field values typical of the operation of these devices are reviewed.

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KIM, K. W., V. A. KOCHELAP, V. N. SOKOLOV i S. M. KOMIRENKO. "QUASI-BALLISTIC AND OVERSHOOT TRANSPORT IN GROUP III-NITRIDES". International Journal of High Speed Electronics and Systems 14, nr 01 (marzec 2004): 127–54. http://dx.doi.org/10.1142/s0129156404002272.

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We analyze steady-state and transient electron transport in the group III-nitride materials at high and ultra-high electric fields for different electron concentration regimes. At high electron concentrations where the electron distribution function assumes a shifted Maxwellian, we investigate different time-dependent transient transport regimes through the phase-plane anyalysis. Unexpected electron heating pattern is observed during the velocity overshoot process with a moderate electron temperature near the peak velocity followed by rapid increase in the deceleration period. For short nitride diodes, space-charge limited transport is considered by taking into account the self-consistent field. In this case, the overshoot is weaker and the electron heating in the region of the peak velocity is greater than that found for time-dependent problem. The transient processes are extended to sufficiently larger distances as well. When the electron concentration is small, we propose a model which accounts the main features of injected electrons in a short device with high fields. The electron velocity distribution over the device is found as a function of the field. It is demonstrated that in high fields the electrons are characterized by the extreme distribution function with the population inversion.

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41

Li, Kexin, i Shaloo Rakheja. "Modeling and Simulation of Quasi-Ballistic III-Nitride Transistors for RF and Digital Applications". International Journal of High Speed Electronics and Systems 28, nr 01n02 (marzec 2019): 1940011. http://dx.doi.org/10.1142/s0129156419400111.

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This paper presents a self-consistent analytic model to describe the current-voltage (I-V) and charge-voltage (Q-V) behavior of quasi-ballistic III-nitride transistors. We focus on two types of transistor geometries: (i) high electron mobility transistors (HEMTs) suitable for radio frequency (RF) applications and (ii) nanowire field-effect transistors (FETs) for digital applications. Our core model is based on Landauer transport theory which is combined with the calculation of charge density and velocity of charges at the top-of-the-barrier in the transistor. The effect of extrinsic device features, such as the nonlinearity of access regions and Joule heating at high currents, are included in the static I-V model. In the case of the dynamic Q-V model, we calculate intrinsic terminal charges by approximating the solution of the 2D Poisson equation in the channel over a broad bias range. The effect of fringing capacitances, prominently inner-fringing capacitance that varies nonlinearly with the gate bias, is included in our Q-V model. We amend the model electrostatics and the description of source/drain rectifying contacts in our core model to represent the I-V characteristics of III-nitride nanowire FETs. The model shows excellent match against experimentally and numerically measured characteristics of GaN transistors with gate lengths ranging from 42 nm to 274 nm. With only 38 input parameters, most of which are extracted based on straightforward device characterization, our model can be used for device-circuit co-design and optimization using a standard hierarchical circuit simulator.

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Ho, W. Y., W. K. Fong, Charles Surya, K. Y. Tong, L. W. Lu i W. K. Ge. "Characterization of Hot-Electron Effects on Flicker Noise in III-V Nitride Based Heterojunctions". MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 560–64. http://dx.doi.org/10.1557/s1092578300003045.

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We report experiments on hot-electron stressing in commercial III-V nitride based heterojunction light-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the I-V characteristics, electroluminescence, Deep-Level Transient Fourier Spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics. The room temperature electroluminescence of the devices exhibited 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by measuring the Deep-Level Transient Fourier Spectroscopy, which indicated an increase in the density of deep-traps from 2.7 × 1013 cm−3 to 4.21 × 1013 cm−3 at E1 = EC − 1.1eV. The result is consistent with our study of 1/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. Our experiments show large increase in both the interface traps and deep-levels resulted from hot-carrier stressing.

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El-Ghoroury, Hussein S., Mikhail V. Kisin i Chih-Li Chuang. "III-Nitride Multi-Quantum-Well Light Emitting Structures with Selective Carrier Injection". Applied Sciences 9, nr 18 (15.09.2019): 3872. http://dx.doi.org/10.3390/app9183872.

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Incorporation into the multi-layered active region of a semiconductor light-emitting structure specially designed intermediate carrier blocking layers (IBLs) allows efficient control over the carrier injection distribution across the structure’s active region to match the application-driven device injection characteristics. This approach has been successfully applied to control the color characteristics of monolithic multi-color light-emitting diodes (LEDs). We further exemplify the method’s versatility by demonstrating the IBL design of III-nitride multiple-quantum-well (MQW) light-emitting diode with active quantum wells uniformly populated at LED operational current.

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Chandrasekar, Hareesh. "Substrate Effects in GaN-on-Silicon RF Device Technology". International Journal of High Speed Electronics and Systems 28, nr 01n02 (marzec 2019): 1940001. http://dx.doi.org/10.1142/s0129156419400019.

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The influence of the semiconducting Si substrate on the performance of GaN-on-Si RF technology is reviewed. Firstly, the formation of a parasitic conduction channel at the substrate-epitaxy interface is discussed in terms of its physical mechanism and its influence on RF loss, followed by schemes to minimize this effect. Secondly, it is shown that the presence of the parallel channel serves to backbias the III-nitride epitaxial stack and lead to current collapse even on the highly-resistive Si substrates used for RF device fabrication, analogous to GaN-on-doped Si power devices. Strategies to mitigate this issue are also presented and critically compared. Thirdly, thermal generation of carriers in Si at elevated operating temperatures leading to increased substrate loss is quantified, also followed by a discussion of possible techniques to reduce its influence on RF loss.

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45

Khafagy, Khaled H., Tarek M. Hatem i Salah M. Bedair. "Modelling of III-Nitride Epitaxial Layers Grown on Silicon Substrates with Low Dislocation-Densities". MRS Advances 4, nr 13 (2019): 755–60. http://dx.doi.org/10.1557/adv.2019.49.

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ABSTRACTLarge lattice and thermal expansion coefficients mismatches between III-Nitride (III N) epitaxial layers and their substrates inevitably generate defects on the interfaces. Such defects as dislocations affect the reliability, life time, and performance of photovoltaic (PV) devices. High dislocation densities in epitaxial layer generate higher v-shaped pits densities on the layer top surface that also directly affect the device performance. Therefore, using an approach such as the embedded void approach (EVA) for defects reduction in the epitaxial layers is essential. EVA relies on the generation of high densities of embedded microvoids (∼108/cm2), with ellipsoidal shapes. These tremendous number of microvoids are etched near the interface between the III N thin-film and its substrate where the dislocation densities present with higher values.This article used a 3-D constitutive model that accounts the crystal plasticity formulas and specialized finite element (FE) formulas to model the EVA in multi-junction PV and therefore to study the effect of the embedded void approach on the defects reduction. Mesh convergence and 2-D analytical solution validation is conducted with accounting thermal stresses. Several aspect and volume ratios of the embedded microvoids are used to optimize the microvoid dimensions.

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46

Kuball, M., M. Benyoucef, F. H. Morrissey i C. T. Foxon. "Focused Ion Beam Etching of Nanometer-Size GaN/AlGaN Device Structures and their Optical Characterization by Micro-Photoluminescence/Raman Mapping". MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 950–56. http://dx.doi.org/10.1557/s1092578300005317.

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We report on the nano-fabrication of GaN/AlGaN device structures using focused ion beam (FIB) etching, illustrated on a GaN/AlGaN heterostructure field effect transistor (HFET). Pillars as small as 20nm to 300nm in diameter were fabricated from the GaN/AlGaN HFET. Micro-photoluminescence and UV micro-Raman maps were recorded from the FIB-etched pattern to assess its material quality. Photoluminescence was detected from 300nm-size GaN/AlGaN HFET pillars, i.e., from the AlGaN as well as the GaN layers in the device structure, despite the induced etch damage. Properties of the GaN and the AlGaN layers in the FIB-etched areas were mapped using UV Micro-Raman spectroscopy. Damage introduced by FIB-etching was assessed. The fabricated nanometer-size GaN/AlGaN structures were found to be of good quality. The results demonstrate the potential of FIB-etching for the nano-fabrication of III-V nitride devices.

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47

Onyeaju, M. C., A. N. Ikot, C. A. Onate, E. Aghemenloh i H. Hassanabadi. "Electronic states in core/shell GaN/YxGa1−xN quantum well (QW) with the modified Pöschl–Teller plus Woods–Saxon potential in the presence of electric field". International Journal of Modern Physics B 31, nr 15 (7.03.2017): 1750119. http://dx.doi.org/10.1142/s0217979217501193.

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The electronic states of a core/shell quantum well (QW) system confined in a modified Pöschl–Teller (PT) plus Woods–Saxon (WS) potential in the presence of electric field are studied with the III-Nitride group owing to their wide bandgap for device applications. The bandgap energy in this regard is obtained by solving analytically the Schrödinger wave equation with the Pekeris-type approximation to the centrifugal term.

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48

Mi, Zetian. "(Invited) Artificial Photosynthesis on III-Nitride Nanowire Arrays". ECS Meeting Abstracts MA2018-01, nr 31 (13.04.2018): 1850. http://dx.doi.org/10.1149/ma2018-01/31/1850.

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High efficiency artificial photosynthesis, that can convert solar energy directly into chemical fuels, has been extensively investigated. To date, however, success in finding abundant visible-light active photocatalyst has been very limited. Recently, metal-nitrides (e.g. InGaN) have attracted considerable attention for applications in artificial photosynthesis, due to their excellent stability and tunable energy bandgap across nearly the entire solar spectrum. Moreover, InGaN is the only known material whose energy bandgap can straddle the redox potential of water under deep visible and near-infrared light irradiation. In this context, we have investigated the design, fabrication, and performance characterization of multi-band InGaN/GaN nanowire photocatalysts and photoelectrodes for solar water splitting and carbon dioxide reduction. In this work, InGaN nanowires are grown on Si substrate by molecular beam epitaxy. The water splitting reaction takes place on the nonpolar surface (m-planes) of InGaN nanowire photocatalysts. By optimizing the surface charge properties through controlled Mg dopant incorporation, the efficiency for solar-to-hydrogen conversion is enhanced by nearly two orders of magnitude. The absorbed photon conversion efficiency reaches ~90% with optimum Mg doping concentration. The significantly enhanced efficiency is directly related to the optimized surface electronic properties that lead to both efficient water oxidation and proton reduction. A solar-to-hydrogen conversion efficiency of 3.3% and stability >500 hours was demonstrated in photocatalytic overall water splitting. High stability of these nanowires is attributed to the N-rich surfaces of GaN nanowire structures, which protects against photocorrosion and oxidation. We have further demonstrated multi-band InGaN/GaN nanowire photoelectrodes monolithically integrated on a Si solar cell wafer. The tandem PEC device consists of a planar n+-p Si solar cell wafer and p-InGaN nanowire segments. The p-InGaN nanowire arrays are designed to absorb the ultraviolet and visible solar spectrum. The remaining photons with wavelengths up to 1.1 µm are absorbed by the underlying planar Si p-n junction. Such a monolithically integrated photocathode promises solar-to-hydrogen conversion efficiency >20%. With the use of such a photoelectrode, we have also demonstrated that syngas, a key feedstock to produce methanol and liquid fuels in industry, can be produced from a CO2 and H2O with a benchmark turnover number of 1330 and a desirable CO/H2 ratio of 1:2. Work is currently in progress to achieve high efficiency syngas and methanol generation in an aqueous photoelectrochemical cell.

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SIMIN, G., M. ASIF KHAN, M. S. SHUR i R. GASKA. "INSULATED GATE III-N HETEROSTRUCTURE FIELD-EFFECT TRANSISTORS". International Journal of High Speed Electronics and Systems 14, nr 01 (marzec 2004): 197–224. http://dx.doi.org/10.1142/s0129156404002302.

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Unique materials properties of GaN -based semiconductors that make them promising for high-power high-temperature applications are high electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown field, and low thermal impedance (when grown over SiC or bulk AlN substrates). The chemical inertness of nitrides is another key property. An AlGaN / GaN Heterostructure Field Effect Transistor (HFET) has been a topic of intensive investigations since the first report in 1991 [1]. Several groups demonstrated high power operation of AlGaN / GaN HFETs at microwave frequencies [2,3,4], including a 100 W output power single chip amplifier developed by Cree, Inc. and devices with 100 GHz cut-off frequency reported in [5]. However, in spite of impressive achievements, the potential of nitride based HFETs has not been fully realized as yet. The RF powers expected from the fundamental properties of nitride based materials significantly exceed the experimental data. One of the key problems limiting the HFETs RF characteristics is high gate leakage currents causing DC and RF parameter degradation. When the gate voltage goes positive the forward leakage current shunts the gate-channel capacitance and thus limits the maximum device current. When the gate voltage is negative, high voltage drop between the gate and the drain causes premature breakdown and thus limits maximum applied drain voltage. In addition, gate leakage currents increase the device sub-threshold currents, which decrease the achievable amplitude of the RF output. These limitations become even more severe at high ambient temperatures. The characteristics of III-N HFETs can be considerably improved by implementing a new approach, which results from the demonstration of good quality of SiO 2/ AlGaN and Si 3 N 4/ AlGaN interfaces. This approach opens up a way to fabricate insulated gate heterostructure field-effect transistors (IGHFETs), which have the gate leakage currents several orders of magnitude below those of regular HFETs, and exhibit better linearity and higher channel saturation currents. In this chapter, we describe design, characterization and applications of these novel devices.

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Bulashevich, Kirill, Sergey Konoplev i Sergey Karpov. "Effect of Die Shape and Size on Performance of III-Nitride Micro-LEDs: A Modeling Study". Photonics 5, nr 4 (27.10.2018): 41. http://dx.doi.org/10.3390/photonics5040041.

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Flip-chip truncated-pyramid-shaped blue micro-light-emitting diodes (μ-LEDs), with different inclinations of the mesa facets to the epitaxial layer plane, are studied by simulations, implementing experimental information on temperature-dependent parameters and characteristics of large-size devices. Strong non-monotonous dependence of light extraction efficiency (LEE) on the inclination angle is revealed, affecting, remarkably, the overall emission efficiency. Without texturing of emitting surfaces, LEE to air up to 54.4% is predicted for optimized shape of the μ-LED dice, which is higher than that of conventional large-size LEDs. The major factors limiting the μ-LED performance are identified, among which, the most critical are the optical losses originated from incomplete light reflection from metallic electrodes and the high p-contact resistance caused by its small area. Optimization of the p-electrode dimensions enables further improvement of high-current wall-plug efficiency of the devices. The roles of surface recombination, device self-heating, current crowding, and efficiency droop at high current densities, in limitation of the μ-LED efficiency, are assessed. A novel approach implementing the characterization data of large-size LED as the input information for simulations is tested successfully.

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