Journal articles: 'Ga2O3 epitaxial growth and optoelectronic devices'

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Nelson, Erik C., Neville L. Dias, Kevin P. Bassett, Simon N. Dunham, Varun Verma, Masao Miyake, Pierre Wiltzius, et al. "Epitaxial growth of three-dimensionally architectured optoelectronic devices." Nature Materials 10, no. 9 (July 24, 2011): 676–81. http://dx.doi.org/10.1038/nmat3071.

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An, Yuxin, Liyan Dai, Ying Wu, Biao Wu, Yanfei Zhao, Tong Liu, Hui Hao, et al. "Epitaxial growth of β-Ga2O3 thin films on Ga2O3 and Al2O3 substrates by using pulsed laser deposition." Journal of Advanced Dielectrics 09, no. 04 (August 2019): 1950032. http://dx.doi.org/10.1142/s2010135x19500322.

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In this work, we have successfully grown high quality epitaxial [Formula: see text]-Ga2O3 thin films on [Formula: see text]-Ga2O3 (100) and Al2O3(0001) substrates using pulsed laser deposition (PLD). By optimizing temperature and oxygen pressure, the best conditions were found to be 650–700∘C and 0.5[Formula: see text]Pa. To further improve the quality of hetero-epitaxial [Formula: see text]-Ga2O3, the sapphire substrates were pretreated for atomic terraced surface by chemical cleaning and high temperature annealing. From the optical transmittance measurements, the films grown at 600–750∘C exhibit a clear absorption edge at deep ultraviolet region around 250–275[Formula: see text]nm wavelength. High resolution transmission electron microscope (HRTEM) images and X-ray diffraction (XRD) patterns demonstrate that [Formula: see text]-Ga2O3(-201)//Al2O3(0001) epitaxial texture dominated the epitaxial oxide films on sapphire substrate, which opens up the possibilities of high power electric devices.

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Lu, Chao, Lei Gao, Fanqi Meng, Qinghua Zhang, Lihong Yang, Zeng Liu, Mingtong Zhu, et al. "Epitaxial growth of a β-Ga₂O₃ (−201)-oriented thin film on a threefold symmetrical SrTiO₃ (111) substrate for heterogeneous integration." Journal of Applied Physics 133, no. 4 (January 28, 2023): 045306. http://dx.doi.org/10.1063/5.0112175.

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Epitaxial growth of a wide bandgap semiconductor β-Ga2O3 thin film with high crystal quality plays a decisive role in constructing optical and electronic devices. However, except for the native substrate, the scarcity of appropriate non-native substrates or the poor crystallization of the deposit in thin film growth severely limits the fabrication and applicability of the final heterostructures and devices. Here, by taking the consistent symmetry and closely matched atomic spacing between β-Ga2O3 (−201) and the cubic perovskite (111)-oriented plane of SrTiO3, we realize the epitaxial growth of single crystal β-Ga2O3 (−201) thin films on the SrTiO3 (111) substrate by the pulsed laser deposition method, as confirmed by wide-range reciprocal-space mapping and high-resolution scanning transmission electron microscopy. The fabricated β-Ga2O3 (−201) photodetector device on the SrTiO3 (111) substrate exhibits excellent ultraviolet optical detection performance with large on/off switching ratios and a fast response speed. Moreover, the β-Ga2O3/SrTiO3 (111) heterojunction shows type-II heterostructure characteristics for energy band alignment, which displays superior ability for electron–hole pairs separation with large conduction and small valance band offsets of 1.68 and 0.09 eV, respectively. The results offer us a new way to obtain high-quality β-Ga2O3 (−201) thin film heterostructures on cubic SrTiO3 (111) substrates and fabricate β-Ga2O3-based optical and electronic devices.

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Gogova, Daniela, Misagh Ghezellou, Dat Q. Tran, Steffen Richter, Alexis Papamichail, Jawad ul Hassan, Axel R. Persson, et al. "Epitaxial growth of β-Ga₂O₃ by hot-wall MOCVD." AIP Advances 12, no. 5 (May 1, 2022): 055022. http://dx.doi.org/10.1063/5.0087571.

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The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of β-Ga2O3. Epitaxial β-Ga2O3 layers at high growth rates (above 1 μm/h), at low reagent flows, and at reduced growth temperatures (740 °C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial β-Ga2O3 layers are demonstrated with a [Formula: see text]01 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown ([Formula: see text]01) β-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of β-Ga2O3.

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Guzilova, L. I., A. S. Grashchenko, and V. I. Nikolaev. "THE STUDY OF MECHANICAL DEFORMATION RESISTANCE OF α-Ga2O3 EPITAXIAL LAYERS USING THE NANOINDENTATION TECHNIQUE." Frontier materials & technologies, no. 4 (2021): 7–16. http://dx.doi.org/10.18323/2782-4039-2021-4-7-16.

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Gallium oxide (Ga2O3) is a wide-band semiconducting material with an energy gap width Eg=4.8–5.0 eV, high conductivity (λ~10.9–27.0 W/(m·K)), and radiation and chemical resistance. Its energy gap width and conductivity allow in the future using the material in the structures of power equipment and optoelectronic devices to increase their energy performance, i.e. to decrease heating and increase productive capacity. Radiation resistance, high breakdown field, and optical asymmetry of Ga2O3 make it attractive for application when designing UV-photoelectric receivers and space systems. The electrical and optical properties of Ga2O3 are amply studied, but there are no systematic data on its physical and mechanical properties (hardness, Young’s modulus, and crack resistance). The paper investigated the deformation in α-Ga2O3 epitaxial layers during nanoindentation. For indentation, the authors used NanoTest (Micro Materials Ltd.) hardness meter. The surface (0001) of α-Ga2O3 crystalline layers produced in the process of chloride gas epitaxy on sapphire (Al2O3) substrates with basic (0001) orientation was investigated. For the first time, the authors experimentally obtained the values of α-Ga2O3 hardness and Young’s modulus using the Oliver-Farr method. The dependences of the indentation load on the penetration depth demonstrated the deviation from linearity, including stress relaxation coming from the pop-in phenomenon. The average values of nanohardness H and Young’s modulus E were 17 and 281 GPa, respectively. The obtained H and E values demonstrate higher characteristics compared to the formerly studied β-Ga2O3 epitaxial layers. This discrepancy can be explained by the more close-packed arrangement of the α-Ga2O3 structure (the corundum type) than one of monoclinic β-Ga2O3. The study shows that α-Ga2O3 leaves the majority of semiconducting materials behind in its mechanical properties conceding only to gallium nitride (GaN) and sapphire (Al2O3)

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Vescan, L., T. Stoica, M. Goryll, and K. Grimm. "Selective epitaxial growth of strained SiGe/Si for optoelectronic devices." Materials Science and Engineering: B 51, no. 1-3 (February 1998): 166–69. http://dx.doi.org/10.1016/s0921-5107(97)00253-5.

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Zhao, Mei, Manman Liu, Youqing Dong, Chao Zou, Keqin Yang, Yun Yang, Lijie Zhang, and Shaoming Huang. "Epitaxial growth of two-dimensional SnSe2/MoS2 misfit heterostructures." Journal of Materials Chemistry C 4, no. 43 (2016): 10215–22. http://dx.doi.org/10.1039/c6tc03406c.

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van der Waals (vdWs) heterostructures, obtained by vertically stacking two-dimensional layered materials upon each other, appear particularly promising for future atomically thin electronic and optoelectronic devices and attract a great deal of attention due to their diverse functionalities.

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Tak, Bhera Ram, Ming-Min Yang, Marin Alexe, and Rajendra Singh. "Deep-Level Traps Responsible for Persistent Photocurrent in Pulsed-Laser-Deposited β-Ga2O3 Thin Films." Crystals 11, no. 9 (August 30, 2021): 1046. http://dx.doi.org/10.3390/cryst11091046.

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Gallium oxide (β-Ga2O3) is emerging as a promising wide-bandgap semiconductor for optoelectronic and high-power electronic devices. In this study, deep-level defects were investigated in pulsed-laser-deposited epitaxial films of β-Ga2O3. A deep ultraviolet photodetector (DUV) fabricated on β-Ga2O3 film showed a slow decay time of 1.58 s after switching off 250 nm wavelength illumination. Generally, β-Ga2O3 possesses various intentional and unintentional trap levels. Herein, these traps were investigated using the fractional emptying thermally stimulated current (TSC) method in the temperature range of 85 to 473 K. Broad peaks in the net TSC curve were observed and further resolved to identify the characteristic peak temperature of individual traps using the fractional emptying method. Several deep-level traps having activation energies in the range of 0.16 to 1.03 eV were identified. Among them, the trap with activation energy of 1.03 eV was found to be the most dominant trap level and it was possibly responsible for the persistent photocurrent in PLD-grown β-Ga2O3 thin films. The findings of this current work could pave the way for fabrication of high-performance DUV photodetectors.

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Hasan, Md Nazmul, Edward Swinnich, and Jung-Hun Seo. "Recent Progress in Gallium Oxide and Diamond Based High Power and High-Frequency Electronics." International Journal of High Speed Electronics and Systems 28, no. 01n02 (March 2019): 1940004. http://dx.doi.org/10.1142/s0129156419400044.

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In recent years, the emergence of the ultrawide‐bandgap (UWBG) semiconductor materials that have an extremely large bandgap, exceeding 5eV including AlGaN/AlN, diamond, β-Ga2O3, and cubic BN, provides a new opportunity in myriad applications in electronic, optoelectronic and photonics with superior performance matrix than conventional WBG materials. In this review paper, we will focus on high power and high frequency devices based on two most promising UWBG semiconductors, β-Ga2O3 and diamond among various UWBG semiconductor devices. These two UWBG semiconductors have gained substantial attention in recent years due to breakthroughs in their growth technique as well as various device engineering efforts. Therefore, we will review recent advances in high power and high frequency devices based on β-Ga2O3 and diamond in terms of device performance metrics such as breakdown voltage, power gain, cut off frequency and maximum operating frequency.

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Skipper, Alec M., Priyanka Petluru, Daniel J. Ironside, Ashlee M. García, Aaron J. Muhowski, Daniel Wasserman, and Seth R. Bank. "All-epitaxial, laterally structured plasmonic materials." Applied Physics Letters 120, no. 16 (April 18, 2022): 161103. http://dx.doi.org/10.1063/5.0094677.

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Optoelectronic devices in the mid-infrared have attracted significant interest due to numerous potential applications in communications and sensing. Molecular beam epitaxial (MBE) growth of highly doped InAs has emerged as a promising “designer metal” platform for the plasmonic enhancement of mid-infrared devices. However, while typical plasmonic materials can be patterned to engineer strong localized resonances, the lack of lateral control in conventional MBE growth makes it challenging to create similar structures compatible with monolithically grown plasmonic InAs. To this end, we report the growth of highly doped InAs plasmonic ridges for the localized resonant enhancement of mid-IR emitters and absorbers. Furthermore, we demonstrate a method for regaining a planar surface above plasmonic corrugations, creating a pathway to epitaxially integrate these structures into active devices that leverage conventional growth and fabrication techniques.

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Wang, Chao, David Barba, Haiguang Zhao, Xin Tong, Zhiming Wang, and Federico Rosei. "Epitaxial growth and defect repair of heterostructured CuInSexS2−x/CdSeS/CdS quantum dots." Nanoscale 11, no. 41 (2019): 19529–35. http://dx.doi.org/10.1039/c9nr06110j.

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Kim, Kyoung-Ho, Minh-Tan Ha, Heesoo Lee, Minho Kim, Okhyun Nam, Yun-Ji Shin, Seong-Min Jeong, and Si-Young Bae. "Microstructural Gradational Properties of Sn-Doped Gallium Oxide Heteroepitaxial Layers Grown Using Mist Chemical Vapor Deposition." Materials 15, no. 3 (January 29, 2022): 1050. http://dx.doi.org/10.3390/ma15031050.

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This study examined the microstructural gradation in Sn-doped, n-type Ga2O3 epitaxial layers grown on a two-inch sapphire substrate using horizontal hot-wall mist chemical vapor deposition (mist CVD). The results revealed that, compared to a single Ga2O3 layer grown using a conventional single-step growth, the double Ga2O3 layers grown using a two-step growth process exhibited excellent thickness uniformity, surface roughness, and crystal quality. In addition, the spatial gradient of carrier concentration in the upper layer of the double layers was significantly affected by the mist flow velocity at the surface, regardless of the dopant concentration distribution of the underlying layer. Furthermore, the electrical properties of the single Ga2O3 layer could be attributed to various scattering mechanisms, whereas the carrier mobility of the double Ga2O3 layers could be attributed to Coulomb scattering owing to the heavily doped condition. It strongly suggests the two-step-grown, lightly-Sn-doped Ga2O3 layer is feasible for high power electronic devices.

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Tang, Wenbo, Yongjian Ma, Xiaodong Zhang, Xin Zhou, Li Zhang, Xuan Zhang, Tiwei Chen, et al. "High-quality (001) β-Ga₂O₃ homoepitaxial growth by metalorganic chemical vapor deposition enabled by in situ indium surfactant." Applied Physics Letters 120, no. 21 (May 23, 2022): 212103. http://dx.doi.org/10.1063/5.0092754.

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(001) β-Ga2O3 homoepitaxy on commercially available large-size (001) β-Ga2O3 substrates remains a significant challenge for the wide bandgap semiconductor community. In this Letter, high-quality homoepitaxial (001) β-Ga2O3 films were grown via metalorganic chemical vapor deposition (MOCVD) with the assistance of an in situ indium surfactant, where the growth modes and mechanisms were also elucidated. During the growth of β-Ga2O3, an etching process occurred by the desorption of the suboxide Ga2O, resulting in rough surface morphology with streaky grooves oriented along the [010] direction. It is postulated that the parallel grooves were associated with the surface desorption and anisotropic diffusion characteristics of β-Ga2O3. To suppress the desorption, indium surfactant was introduced into the growth environment. A 2D-like growth feature was prompted subsequently by the coadsorption of In and Ga atoms, accompanied by relatively smooth surface morphology. The crystal quality had no degradation despite the incorporation of indium in the epitaxial film. The O II peak of the β-Ga2O3 film shifted ∼0.5 eV toward higher binding energy due to an increasing number of oxygen vacancies originating from the indium incorporation. This work provides a systemic investigation on the growth of high-quality (001) β-Ga2O3 homoepitaxial films by MOCVD, which is critical for the development of β-Ga2O3 electronic devices for future power switching and RF applications.

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Yadav, Asha, Bo Fu, Stephanie Nicole Bonvicini, Linh Quy Ly, Zhitai Jia, and Yujun Shi. "β-Ga2O3 Nanostructures: Chemical Vapor Deposition Growth Using Thermally Dewetted Au Nanoparticles as Catalyst and Characterization." Nanomaterials 12, no. 15 (July 28, 2022): 2589. http://dx.doi.org/10.3390/nano12152589.

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β-Ga2O3 nanostructures, including nanowires (NWs), nanosheets (NSHs), and nanorods (NRs), were synthesized using thermally dewetted Au nanoparticles as catalyst in a chemical vapor deposition process. The morphology of the as-grown β-Ga2O3 nanostructures depends strongly on the growth temperature and time. Successful growth of β-Ga2O3 NWs with lengths of 7–25 μm, NSHs, and NRs was achieved. It has been demonstrated that the vapor–liquid–solid mechanism governs the NW growth, and the vapor–solid mechanism occurs in the growth of NSHs and NRs. The X-ray diffraction analysis showed that the as-grown nanostructures were highly pure single-phase β-Ga2O3. The bandgap of the β-Ga2O3 nanostructures was determined to lie in the range of 4.68–4.74 eV. Characteristic Raman peaks were observed with a small blue and red shift, both of 1–3 cm−1, as compared with those from the bulk, indicating the presence of internal strain and defects in the as-grown β-Ga2O3 nanostructures. Strong photoluminescence emission in the UV-blue spectral region was obtained in the β-Ga2O3 nanostructures, regardless of their morphology. The UV (374–377 nm) emission is due to the intrinsic radiative recombination of self-trapped excitons present at the band edge. The strong blue (404–490 nm) emissions, consisting of five bands, are attributed to the presence of the complex defect states in the donor (VO) and acceptor (VGa or VGa–O). These β-Ga2O3 nanostructures are expected to have potential applications in optoelectronic devices such as tunable UV–Vis photodetectors.

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Wang, Xiaojie, Wenxiang Mu, Jiahui Xie, Jinteng Zhang, Yang Li, Zhitai Jia, and Xutang Tao. "Rapid epitaxy of 2-inch and high-quality α-Ga₂O₃ films by mist-CVD method." Journal of Semiconductors 44, no. 6 (June 1, 2023): 062803. http://dx.doi.org/10.1088/1674-4926/44/6/062803.

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Abstract High thickness uniformity and large-scale films of α-Ga2O3 are crucial factors for the development of power devices. In this work, a high-quality 2-inch α-Ga2O3 epitaxial film on c-plane sapphire substrates was prepared by the mist-CVD method. The growth rate and phase control mechanisms were systematically investigated. The growth rate of the α-Ga2O3 films was limited by the evaporation of the microdroplets containing gallium acetylacetonate. By adjusting the substrate position (z) from 80 to 50 mm, the growth rate was increased from 307 nm/h to 1.45 μm/h when the growth temperature was fixed at 520 °C. When the growth temperature exceeded 560 °C, ε-Ga2O3 was observed to form at the edges of 2-inch sapphire substrate. Phase control was achieved by adjusting the growth temperature. When the growth temperature was 540 °C and the substrate position was 50 mm, the full-width at half maximum (FWHM) of the rocking curves for the (0006) and (10-14) planes were 0.023° and 1.17°. The screw and edge dislocations were 2.3 × 106 and 3.9 × 1010 cm-2, respectively. Furthermore, the bandgaps and optical transmittance of α-Ga2O3 films grown under different conditions were characterized utilizing UV-visible and near-IR scanning spectra.

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Chuai, Ya-Hui, Hong-Zhi Shen, Ya-Dan Li, Bing Hu, Yu Zhang, Chuan-Tao Zheng, and Yi-Ding Wang. "Epitaxial growth of highly infrared-transparent and conductive CuScO2 thin film by polymer-assisted-deposition method." RSC Advances 5, no. 61 (2015): 49301–7. http://dx.doi.org/10.1039/c5ra07743e.

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Sun, Yuan Yuan, Xi He Zhang, Qiu Rui Jia, Zheng Li, and Shi Bo Liu. "Research on the Preparation Technology of GaN Ultraviolet Photoelectric Detector." Advanced Materials Research 717 (July 2013): 205–9. http://dx.doi.org/10.4028/www.scientific.net/amr.717.205.

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GaN semiconductor was one of the most promising semiconductor materials with direct wide band gap transition. It was regarded as one of the most desirable materials to prepare short wavelength optoelectronic devices for the good optoelectronic properties and excellent mechanical behavior. In this paper, n and p-type GaN films were prepared on Al2O3 substrates by MOCVD. Through the optimization of parameters, we obtained effective in doped Mg and carrier concentration for 1019. MSM structural ultraviolet photoelectric devices were prepared on GaN film by two step epitaxy growth method. The highest transmittance and best epitaxial growth quality has been gained at 570°C for buffer layer of the samples.

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Cheng, Lu, Yanlin Wu, Wenbin Zhong, Duanyang Chen, Hongji Qi, and Wei Zheng. "Photophysics of β-Ga₂O₃: Phonon polaritons, exciton polaritons, free-carrier absorption, and band-edge absorption." Journal of Applied Physics 132, no. 18 (November 14, 2022): 185704. http://dx.doi.org/10.1063/5.0118843.

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Monoclinic gallium oxide ( β-Ga2O3) has attracted much attention from the fields of optoelectronic and electronic devices owing to the properties of wide bandgap, great breakdown field strength, as well as the economic advantages of low-cost growth of large-size single crystals. Here, the basic photophysical properties including absorption (free-carrier absorption and band-edge absorption) and reflection (phonon polaritons and exciton polaritons) of differently doped β-Ga2O3 with diverse carrier concentrations are studied in detail. The unpolarized reflection spectra of differently doped β-Ga2O3 crystals are well fitted based on the non-polarized reflection model. Besides, according to analysis, the longitudinal–transverse splitting energy of β-Ga2O3 direct excitons is estimated to be as high as 100 meV, reflecting the strong interaction between light and excitons. It is hoped that this work can provide beneficial reference for a comprehensive understanding on the spectral physical characteristics of β-Ga2O3, so as to deepen and expand the basic recognition of this material in the aspect of photophysical properties.

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Bui, Quang Chieu, Ludovic Largeau, Martina Morassi, Nikoletta Jegenyes, Olivia Mauguin, Laurent Travers, Xavier Lafosse, et al. "GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors." Applied Sciences 9, no. 17 (August 28, 2019): 3528. http://dx.doi.org/10.3390/app9173528.

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The development of sensors working in a large range of temperature is of crucial importance in areas such as monitoring of industrial processes or personal tracking using smart objects. Devices integrating GaN/Ga2O3 core/shell nanowires (NWs) are a promising solution for monitoring carbon monoxide (CO). Because the performances of sensors primarily depend on the material properties composing the active layer of the device, it is essential to control them and achieve material synthesis in the first time. In this work, we investigate the synthesis of GaN/Ga2O3 core-shell NWs with a special focus on the formation of the shell. The GaN NWs grown by plasma-assisted molecular beam epitaxy, are post-treated following thermal oxidation to form a Ga2O3-shell surrounding the GaN-core. We establish that the shell thickness can be modulated from 1 to 14 nm by changing the oxidation conditions and follows classical oxidation process: A first rapid oxide-shell growth, followed by a reduced but continuous oxide growth. We also discuss the impact of the atmosphere on the oxidation growth rate. By combining XRD-STEM and EDX analyses, we demonstrate that the oxide-shell is crystalline, presents the β-Ga2O3 phase, and is synthesized in an epitaxial relationship with the GaN-core.

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Murakami, Masanori, Yasuo Koide, Miki Moriyama, and Susumu Tsukimoto. "Development of Electrode Materials for Semiconductor Devices." Materials Science Forum 475-479 (January 2005): 1705–14. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.1705.

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Recent strong demands for optoelectronic communication and portable telephones have encouraged engineers to develop optoelectronic devices, microwave devices, and high-speed devices using heterostructural compound semiconductors. Although the compound crystal growth techniques had reached at a level to control the compositional stoichiometry and crystal defects on a nearly atomic scale by the advanced techniques such as molecular beam epitaxy and metal organic chemical vapor deposition techniques, development of ohmic contact materials (which play a key role to inject external electric current from the metals to the semiconductors) was still on a trial-and-error basis. Our research efforts have been focused to develop, low resistance, refractory ohmic contact materials using the deposition and annealing techniques for n-GaAs, p-ZnSe, InP, p-SiC p-CdTe etc. It was found the growth of homo- or hetero–epitaxial intermediate semiconductor layers (ISL) was essential for low resistance contact formation. The importance of hetero-structural ISL was given taking an example of n-type ohmic contact for GaAs.

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Cirlin, G. E., R. R. Reznik, I. V. Shtrom, A. I. Khrebtov, Yu B. Samsonenko, S. A. Kukushkin, T. Kasama, and N. Akopian. "Hybrid GaAs/AlGaAs nanowire --- quantum dot system for single photon sources." Физика и техника полупроводников 52, no. 4 (2018): 469. http://dx.doi.org/10.21883/ftp.2018.04.45818.07.

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AbstractIII–V nanowires, or a combination of the nanowires with quantum dots, are promising building blocks for future optoelectronic devices, in particular, single-photon emitters, lasers and photodetectors. In this work we present results of molecular beam epitaxial growth of combined nanostructures containing GaAs quantum dots inside AlGaAs nanowires on a silicon substrate showing a new way to combine quantum devices with Si technology.

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Batstone, J. L. "Structural and electronic properties of defects in semiconductors." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 4–5. http://dx.doi.org/10.1017/s0424820100136398.

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The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

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Fu, Wai Yuen, and Hoi Wai Choi. "Progress and prospects of III-nitride optoelectronic devices adopting lift-off processes." Journal of Applied Physics 132, no. 6 (August 14, 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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Kang, T. W., S. H. Park, and T. W. Kim. "Improvement of the crystallinity of GaN epitaxial layers grown on porous Si (100) layers by using a two-step method." Journal of Materials Research 15, no. 12 (December 2000): 2602–5. http://dx.doi.org/10.1557/jmr.2000.0373.

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A new approach was used for combining GaN and porous Si with the goal of producing high-quality GaN epitaxial layers for optoelectronic integrated circuit devices based on Si substrates. Reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), photoluminescence (PL), and Van der Pauw–Hall effect measurements were performed to investigate the structural, optical, and electrical properties of the GaN epitaxial films grown on porous Si(100) by plasma-assisted molecular-beam epitaxy with a two-step method. The RHEED patterns were streaky with clear Kikuchi lines, which was direct evidence for layer-by-layer two-dimensional growth of GaN epitaxial layers on porous Si layers. The XRD curves showed that the grown layers were GaN(0001) epitaxial films. The results of the XRD and the PL measurements showed that the crystallinities of the GaN epilayers grown on porous Si by using a two-step growth were remarkably improved because the porous Si layer reduced the strains in the GaN epilayers by sharing them with the Si substrates. Hall-effect measurements showed that the mobility of the GaN active layer was higher than that of the GaN initial layer. These results indicate that high-quality GaN epitaxial films grown on porous Si(100) by using two-step growth hold promise for potential applications in new kinds of optoelectronic monolithic and ultralarge integrated circuits.

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Spencer, Joseph A., Marko J. Tadjer, Alan G. Jacobs, Michael A. Mastro, John L. Lyons, Jaime A. Freitas, James C. Gallagher, et al. "Activation of implanted Si, Ge, and Sn donors in high-resistivity halide vapor phase epitaxial β-Ga₂O₃:N with high mobility." Applied Physics Letters 121, no. 19 (November 7, 2022): 192102. http://dx.doi.org/10.1063/5.0120494.

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Activation of implanted donors into a highly-resistive, nitrogen-doped homoepitaxial β-Ga2O3 has been investigated. Nitrogen acceptors with the concentration of ∼1017 cm−3 were incorporated during epitaxial growth yielding low-doped (net donor concentration <1014 cm−3) films subsequently implanted with Si, Ge, and Sn. Upon Ohmic contact formation to the implanted regions, sheet resistance values of 314, 926, and 1676 Ω/sq were measured at room temperature for the Si-, Ge-, and Sn-implanted samples, respectively. Room temperature Hall measurements resulted in sheet carrier concentrations and Hall mobilities of 2.13 × 1014 /93, 8.58 × 1013/78, and 5.87 × 1013/63 cm2/(V s), respectively, for these three donor species. Secondary ion mass spectroscopy showed a volumetric dopant concentration of approximately 2 × 1019 cm−3 for the three species, resulting in carrier activation efficiencies of 64.7%, 40.3%, and 28.2% for Si, Ge, and Sn, respectively. Temperature-dependent Hall effect measurements ranging from 15 to 300 K showed a nearly constant carrier concentration in the Si-implanted sample, suggesting the formation of an impurity band indicative of degenerate doping. With a bulk carrier concentration of 1.3 × 1019 cm−3 for the Si implanted sample, a room temperature mobility of 93 cm2/(V s) is among the highest reported in Ga2O3 with a similar carrier concentration. The unimplanted Ga2O3:N regions remained highly resistive after the surrounding areas received implant and activation anneal. These results open the pathway for fabricating Ga2O3 devices through the selective n-type doping in highly resistive epitaxial Ga2O3.

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Chang, P. C., C. L. Yu, Y. W. Jahn, S. J. Chang, and K. H. Lee. "Effect of Growth Temperature on the Indium Incorporation in InGaN Epitaxial Films." Advanced Materials Research 287-290 (July 2011): 1456–59. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1456.

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InxGa1-xN epilayers have been grown by metalorganic chemical vapor deposition (MOCVD) at different temperatures between 740°C to 830°C. The thickness of InGaN film is 50nm for all samples. The incorporation of indium is found to increase with decreasing grown temperature. The optical properties and film quality of the samples have been investigated by photoluminescence (PL) system and X-ray diffraction (XRD). The Full Width at Half Maximum (FWHM) of PL and XRD decreases with increasing the grown temperature. We also found that the peak emission of PL shifts with changing the grown temperature. The effect of temperature on the film properties was determined. This understanding will lead to better quality control of the optoelectronic devices.

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Park, Minseong, Byungjoon Bae, Taegeon Kim, Hyun S. Kum, and Kyusang Lee. "2D materials-assisted heterogeneous integration of semiconductor membranes toward functional devices." Journal of Applied Physics 132, no. 19 (November 21, 2022): 190902. http://dx.doi.org/10.1063/5.0122768.

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Heterogeneous integration techniques allow the coupling of highly lattice-mismatched solid-state membranes, including semiconductors, oxides, and two-dimensional materials, to synergistically fuse the functionalities. The formation of heterostructures generally requires two processes: the combination of crystalline growth and a non-destructive lift-off/transfer process enables the formation of high-quality heterostructures. Although direct atomic interaction between the substrate and the target membrane ensures high-quality growth, the strong atomic bonds at the substrate/epitaxial film interface hinder the non-destructive separation of the target membrane from the substrate. Alternatively, a 2D material-coated compound semiconductor substrate can transfer the weakened (but still effective) surface potential field of the surface through the 2D material, allowing both high-quality epitaxial growth and non-destructive lift-off of the grown film. This Perspective reviews 2D/3D heterogeneous integration techniques, along with applications of III–V compound semiconductors and oxides. The advanced heterogeneous integration methods offer an effective method to produce various freestanding membranes for stackable heterostructures with unique functionalities that can be applied to novel electrical, optoelectronic, neuromorphic, and bioelectronic systems.

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Fu, Houqiang. "(Invited) III-Oxide/III-Nitride Heterostructures for Power Electronics and Optoelectronics Applications." ECS Meeting Abstracts MA2022-02, no. 34 (October 9, 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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Leung, Benjamin, Jie Song, Yu Zhang, Miao-Chan Tsai, Ge Yuan, and Jung Han. "Using the Evolutionary Selection Principle in Selective Area Growth to Achieve Single-Crystalline GaN on SiO2." International Journal of High Speed Electronics and Systems 23, no. 01n02 (March 2014): 1450003. http://dx.doi.org/10.1142/s0129156414500037.

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Conventional epitaxial techniques requires single crystalline substrates to form semiconductor material of desired material quality for device applications. The use of amorphous substrates, in many applications, provides an opportunity to consider new materials and designs, which can fundamentally alter the performance, functionality and/or cost limitations of many optoelectronic devices. Here, a growth process is described to achieve single crystalline GaN material on amorphous SiO2. The evolutionary selection principle in crystal growth is the basis of this technique, and the mechanism is described and analyzed in detail. It is expected that this process can be extended to other semiconductor and substrate combinations, allowing heterogenous integration with functional substrates to produce new classes of semiconductor devices.

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30

Vescan, L. "Facet investigation in selective epitaxial growth of Si and SiGe on (001) Si for optoelectronic devices." Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 16, no. 3 (May 1998): 1549. http://dx.doi.org/10.1116/1.589937.

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31

Kryzhanovskaya, Natalia V., Fedor I. Zubov, Eduard I. Moiseev, Anna S. Dragunova, Konstantin A. Ivanov, Mikhail V. Maximov, Nikolay A. Kaluzhnyy, et al. "On-chip light detection using integrated microdisk laser and photodetector bonded onto Si board." Laser Physics Letters 19, no. 1 (November 29, 2021): 016201. http://dx.doi.org/10.1088/1612-202x/ac3a0f.

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Abstract Characteristics of a compact III–V optocoupler heterogeneously integrated on a silicon substrate and formed by a 31 µm in diameter microdisk (MD) laser with a closely-spaced 50 µm × 200 µm waveguide photodetector are presented. Both optoelectronic devices were fabricated from the epitaxial heterostroctructures with InGaAs/GaAs quantum well-dot layers. The measured dark current density of the photodetector was as low as 2.1 µA cm−2. The maximum link efficiency determined as the ratio of the photodiode photocurrent increment to the increment of the microlaser bias current was 1%–1.4%. The developed heterogeneous integration of III–V devices to silicon boards by Au-Au thermocompression bonding is useful for avoiding the difficulties associated with III–V epitaxial growth on Si and facilitates integration of several devices with different active layers and waveguides. The application of MD lasers with their lateral light output is promising for simplifying requirements for optical loss at III–V/Si interface.

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32

Wang, Yifan, Xuanze Li, Pei Liu, Jing Xia, and Xiangmin Meng. "Epitaxial growth of CsPbBr₃/PbS single-crystal film heterostructures for photodetection." Journal of Semiconductors 42, no. 11 (November 1, 2021): 112001. http://dx.doi.org/10.1088/1674-4926/42/11/112001.

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Abstract Epitaxial high-crystallization film semiconductor heterostructures has been proved to be an effective method to prepare single-crystal films for different functional devices in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as building blocks for heterostructures. Here, the conformal vapor phase epitaxy of CsPbBr3 on PbS single-crystal films is realized to form the CsPbBr3/PbS heterostructures via a two-step vapor deposition process. The structural characterization reveals that PbS substrates and the epilayer CsPbBr3 have clear relationships: CsPbBr3(110) // PbS(100), CsPbBr3[ ] // PbS[001] and CsPbBr3[001] // PbS[010]. The absorption and photoluminescence (PL) characteristics of CsPbBr3/PbS heterostructures show the broadband light absorption and efficient photogenerated carrier transfer. Photodetectors based on the heterostructures show superior photoresponsivity of 15 A/W, high detectivity of 2.65 × 1011 Jones, fast response speed of 96 ms and obvious rectification behavior. Our study offers a convenient method for establishing the high-quality CsPbBr3/PbS single-crystal film heterostructures and providing an effective way for their application in optoelectronic devices.

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33

Wang, Liu, Wenrui Zhang, Ningtao Liu, Tan Zhang, Zilong Wang, Simiao Wu, Zhaolin Zhan, and Jichun Ye. "Epitaxial Growth and Stoichiometry Control of Ultrawide Bandgap ZnGa2O4 Films by Pulsed Laser Deposition." Coatings 11, no. 7 (June 30, 2021): 782. http://dx.doi.org/10.3390/coatings11070782.

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ZnGa2O4 is a promising semiconductor for developing high-performance deep-ultraviolet photodetectors owing to a number of advantageous fundamental characteristics. However, Zn volatilization during the ZnGa2O4 growth is a widely recognized problem that seriously degrades the film quality and the device performance. In this study, we report the synthesis of epitaxial ZnGa2O4 thin films by pulsed laser deposition using a non-stoichiometric Zn1+xGa2O4 target. It is found that supplementing excessive Zn concentration from the target is highly effective to stabilize stochiometric ZnGa2O4 thin films during the PLD growth. The influence of various growth parameters on the phase formation, crystallinity and surface morphology is systematically investigated. The film growth behavior further impacts the resulting optical absorption and thermal conductivity. The optimized epitaxial ZnGa2O4 film exhibits a full width at half maximum value of 0.6 degree for a 120 nm thickness, a surface roughness of 0.223 nm, a band gap of 4.79 eV and a room-temperature thermal conductivity of 40.137 W/(m⋅K). This study provides insights into synthesizing epitaxial ZnGa2O4 films for high performance optoelectronic devices.

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Triplett, Mark, M. Saif Islam, and Dong Yu. "Scanning Photocurrent Microscopy of as-Grown Silicon Nanowire Metallurgical Junctions." MRS Proceedings 1551 (2013): 29–33. http://dx.doi.org/10.1557/opl.2013.991.

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ABSTRACTDuring the epitaxial bottom up growth of nanowire (NW) arrays, occasional kinks in growth direction can lead to intersecting and consequently self-welded crystalline connections between NWs. In order to study these self-welded metallurgical NW junctions, a NW bridge device architecture which requires no post-growth processing was used to grow and stabilize Si NW junctions. Scanning Photocurrent Microscopy (SPCM) was used to study the optoelectronic properties of the NW junctions as well as the characteristics of the NW bridge devices. SPCM measurements show a bias dependent photocurrent (PC) response at the NW junction indicating local band bending at this location. A decay of the PC response away from the junction is also seen in the secondary NW channel ensuring an electrical connection. These junction properties may be important for ensemble NW optical devices.

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35

Yao, Zhonghui, Cheng Jiang, Xu Wang, Hongmei Chen, Hongpei Wang, Liang Qin, and Ziyang Zhang. "Recent Developments of Quantum Dot Materials for High Speed and Ultrafast Lasers." Nanomaterials 12, no. 7 (March 24, 2022): 1058. http://dx.doi.org/10.3390/nano12071058.

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Owing to their high integration and functionality, nanometer-scale optoelectronic devices based on III-V semiconductor materials are emerging as an enabling technology for fiber-optic communication applications. Semiconductor quantum dots (QDs) with the three-dimensional carrier confinement offer potential advantages to such optoelectronic devices in terms of high modulation bandwidth, low threshold current density, temperature insensitivity, reduced saturation fluence, and wavelength flexibility. In this paper, we review the development of the molecular beam epitaxial (MBE) growth methods, material properties, and device characteristics of semiconductor QDs. Two kinds of III-V QD-based lasers for optical communication are summarized: one is the active electrical pumped lasers, such as the Fabry–Perot lasers, the distributed feedback lasers, and the vertical cavity surface emitting lasers, and the other is the passive lasers and the instance of the semiconductor saturable absorber mirrors mode-locked lasers. By analyzing the pros and cons of the different QD lasers by their structures, mechanisms, and performance, the challenges that arise when using these devices for the applications of fiber-optic communication have been presented.

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36

Bhattacharyya, Arkka, Carl Peterson, Takeki Itoh, Saurav Roy, Jacqueline Cooke, Steve Rebollo, Praneeth Ranga, Berardi Sensale-Rodriguez, and Sriram Krishnamoorthy. "Enhancing the electron mobility in Si-doped (010) β-Ga₂O₃ films with low-temperature buffer layers." APL Materials 11, no. 2 (February 1, 2023): 021110. http://dx.doi.org/10.1063/5.0137666.

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We demonstrate a new substrate cleaning and buffer growth scheme in β-Ga2O3 epitaxial thin films using metal–organic vapor phase epitaxy (MOVPE). For the channel structure, a low-temperature (LT, 600 °C) un-doped Ga2O3 buffer was grown, followed by a transition layer to a high-temperature (HT, 810 °C) Si-doped Ga2O3 channel layers without growth interruption. The (010) Ga2O3 Fe-doped substrate cleaning uses solvent cleaning, followed by additional hydrofluoric acid (49% in water) treatment for 30 min before the epilayer growth. This step is shown to compensate the parasitic Si channel at the epilayer–substrate interface that originates from the substrate polishing process or contamination from the ambient. From secondary ion mass spectroscopy (SIMS) analysis, the Si peak atomic density at the substrate interface is found to be several times lower than the Fe atomic density in the substrate—indicating full compensation. The elimination of the parasitic electron channel at the epi–substrate interface was also verified by electrical (capacitance–voltage profiling) measurements. In the LT-grown (600 °C) buffer layers, it is seen that the Fe forward decay tail from the substrate is very sharp, with a decay rate of ∼9 nm/dec. X-ray off-axis rocking curve ω-scans show very narrow full width at half maximum (FWHM) values, similar to the as-received substrates. These channels show record high electron mobility in the range of 196–85 cm2/V⋅s in unintentionally doped and Si-doped films in the doping range of 2 × 1016–1 × 1020 cm−3. Si delta-doped channels were also grown utilizing this substrate cleaning and the hybrid LT buffers. Record high electron Hall mobility of 110 cm2/V⋅s was measured for sheet charge density of 9.2 × 1012 cm−2. This substrate cleaning, combined with the LT buffer scheme, shows the potential of designing Si-doped β-Ga2O3 channels with exceptional transport properties for high-performance Ga2O3-based electron devices.

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37

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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Machtay, N. D., and R. V. Kukta. "Energetics of Epitaxial Island Arrangements on Substrate Mesas." Journal of Applied Mechanics 73, no. 2 (May 14, 2005): 212–19. http://dx.doi.org/10.1115/1.2073327.

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Self-assembly of strained epitaxial deposits (islands) grown on a substrate is a promising route to fabricate nanostructures of significance for electronic and optoelectronic devices. The challenge is to achieve specific island arrangements that are required for device functionality and high performance. This article investigates growth on a topographically patterned substrate as a means to control the arrangement of islands. By taking free energy to consist of elastic energy and surface energy, minimum energy configurations are calculated for islands on a raised substrate mesa. Configurations of one, two, and three islands at different positions on the mesa are considered to determine their relative energies as a function of mesa size, island size, mismatch strain between the island and substrate materials, surface energy, and elastic moduli. Insight is offered on the mechanisms responsible for certain physical observations such as a transition from the formation of multiple islands to a single island as mesa size is reduced.

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39

Vashishtha, Pargam, Pukhraj Prajapat, Lalit Goswami, Aditya Yadav, Akhilesh Pandey, and Govind Gupta. "Stress-Relaxed AlN-Buffer-Oriented GaN-Nano-Obelisks-Based High-Performance UV Photodetector." Electronic Materials 3, no. 4 (December 9, 2022): 357–67. http://dx.doi.org/10.3390/electronicmat3040029.

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Epitaxial GaN nanostructures are developed, and the influence of the AlN buffer layer (temperature modulation) on material characteristics and optoelectronic device application is assessed. The AlN buffer layer was grown on a Si (111) substrate at varying temperatures (770–830 °C), followed by GaN growth using plasma-assisted molecular beam epitaxy. The investigation revealed that the comparatively lower temperature AlN buffer layer was responsible for stress and lattice strain relaxation and was realized as the GaN nano-obelisk structures. Contrarily, the increased temperature of the AlN growth led to the formation of GaN nanopyramidal and nanowax/wane structures. These grown GaN/AlN/Si heterostructures were utilized to develop photodetectors in a metal–semiconductor–metal geometry format. The performance of these fabricated optoelectronic devices was examined under ultraviolet illumination (UVA), where the GaN nano-obelisks-based device attained the highest responsivity of 118 AW−1. Under UVA (325 nm) illumination, the designed device exhibited a high detectivity of 1 × 1010 Jones, noise equivalent power of 1 × 10−12 WHz−1/2, and external quantum efficiency of 45,000%. The analysis revealed that the quality of the AlN buffer layer significantly improved the optoelectronic performance of the device.

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Assali, S., S. Koelling, Z. Abboud, J. Nicolas, A. Attiaoui, and O. Moutanabbir. "500-period epitaxial Ge/Si_0.18Ge_0.82 multi-quantum wells on silicon." Journal of Applied Physics 132, no. 17 (November 7, 2022): 175304. http://dx.doi.org/10.1063/5.0119624.

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Ge/SiGe multi-quantum well heterostructures are highly sought-after for silicon-integrated optoelectronic devices operating in the broad range of the electromagnetic spectrum covering infrared to terahertz wavelengths. However, the epitaxial growth of these heterostructures at a thickness of a few micrometers has been a challenging task due to the lattice mismatch and its associated instabilities resulting from the formation of growth defects. To elucidate these limits, we outline herein a process for the strain-balanced growth on silicon of 11.1/21.5 nm Ge/Si0.18Ge0.82 superlattices (SLs) with a total thickness of 16 μm corresponding to 500 periods. Composition, thickness, and interface width are preserved across the entire SL heterostructure, which is an indication of limited Si–Ge intermixing. High crystallinity and low defect density are obtained in the Ge/Si0.18Ge0.82 layers; however, the dislocation pileup at the interface with the growth substrate induces micrometer-long cracks on the surface. This eventually leads to significant layer tilt in the strain-balanced SL and in the formation of millimeter-long, free-standing flakes. These results confirm the local uniformity of structural properties and highlight the critical importance of threading dislocations in shaping the wafer-level stability of thick multi-quantum well heterostructures required to implement effective silicon-compatible Ge/SiGe photonic devices.

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41

Brown, J. M., S. J. Pearton, R. Caruso, M. Stavola, K. T. Short, D. L. Malm, S. M. Vernon, and W. S. Hobson. "Transmission electron microscopy of epitaxial gallium arsenide grown on a variety of silicon substrates by metallorganic chemical vapor deposition." Proceedings, annual meeting, Electron Microscopy Society of America 45 (August 1987): 342–43. http://dx.doi.org/10.1017/s0424820100126500.

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The growth of GaAs layers on silicon substrates is under extensive investigation with a view to achieving the integration of GaAs-based optoelectronic devices with Si integrated circuit technology. The large lattice mismatch between Si and GaAs (-4%) together with the differences in the thermal expansion coefficients between the two materials results in a highly stressed interface. Several different approaches have been undertaken in attempts to reduce the dislocation density of the GaAs layer. The inclusion of graded composition GaAsP ‘buffer’ layers, intermediate Ge layers and the inclusion of strained layer superlattices in the growth regime have been reported by many workers. Growth of GaAs directly on Si has been reported to yield GaAs heteroepitaxial films suitable for electronic applications such as FETs and low threshold AlGaAs/GaAs double heterostructure injection lasers.

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42

Yang, Duyoung, Byungsoo Kim, Tae Hoon Eom, Yongjo Park, and Ho Won Jang. "Epitaxial Growth of Alpha Gallium Oxide Thin Films on Sapphire Substrates for Electronic and Optoelectronic Devices: Progress and Perspective." Electronic Materials Letters 18, no. 2 (January 6, 2022): 113–28. http://dx.doi.org/10.1007/s13391-021-00333-5.

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43

Xue, Xiaohuan, Jianjun Song, and Rongxi Xuan. "Finite Element Stress Model of Direct Band Gap Ge Implementation Method Compatible with Si Process." Advances in Condensed Matter Physics 2019 (September 16, 2019): 1–9. http://dx.doi.org/10.1155/2019/2096854.

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As an indirect band gap semiconductor, germanium (Ge) can be transformed into a direct band gap semiconductor through some specific modified methods, stress, and alloying effect. Direct band gap-modified Ge semiconductors with a high carrier mobility and radiation recombination efficiency can be applied to optoelectronic devices, which can improve the luminous efficiency dramatically, and they also have the potential application advantages in realizing monolithic optoelectronic integration (MOEI) and become a research hotspot in material fields. Among the various implementations of Ge band gap-type conversion, the related methods that are compatible with the Si process are most promising. It is such a method to etch around the Ge epitaxial layer on the Si substrate and introduce the biaxial tensile stress by SiGe selective filling. However, the influence of the width of the epitaxial layer, Ge composition, and Ge mesa region width on strain distribution and intensity is not clear yet. Accordingly, a finite element stress model of the selective epitaxy-induced direct band gap Ge scheme is established to obtain the material physical and geometric parameters of the Si1−xGex growth region. The result of finite element simulation indicates when the Si1−xGex epitaxial layer is 150–250 nm wide and the Ge composition is 0.3∼0.5, Ge mesa with 20–40 nm in width can be transformed into direct band gap semiconductors in the depth of 0–6 nm. The theoretical results can provide an important theoretical basis for the realization of subsequent related processes.

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44

Shea, B., Q. Sun-Paduano, D. F. Bliss, M. C. Callahan, and C. Sung. "Characterization of Gan/Sapphire Interface and the Buffer Layer by TEM/AFM." Microscopy and Microanalysis 7, S2 (August 2001): 330–31. http://dx.doi.org/10.1017/s1431927600027720.

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Interest in wide band gap III-V nitride semiconductor devices is increasing for optoelectronic and microelectronic device applications. to ensure the highest quality, TEM analysis can characterize the substrate and buffer layer interface. Measurements taken by TEM reveal the density of dislocations/cm2 and the orientation of Burger's vectors. This information allows for changes to be made in deposition rates, temperatures, gas flow rates, and other parameters during the processing.The GaN/sapphire samples grown at AFRL were produced in two consecutive steps, first to provide a thin buffer layer, and the other to grow a lum thick epitaxial film. Both growth steps were prepared using metallic organic chemical vapor deposition (MOCVD) in a vertical reactor. Buffer layers were prepared using a range of temperatures from 525 to 535°C and with a range of flow rates and pressures in order to optimize the nucleation conditions for the epitaxial films.

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45

Nakayama, Yasuo. "(Invited, Digital Presentation) Epitaxial Organic Molecular Interfaces As Well-Ordered Model Systems for Molecular Semiconductor p-n Junctions for Optoelectronic Applications." ECS Meeting Abstracts MA2022-01, no. 13 (July 7, 2022): 907. http://dx.doi.org/10.1149/ma2022-0113907mtgabs.

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Donor-acceptor molecular interfaces are nothing but p-n junctions for organic optoelectronic devices such as organic light emitting diodes and organic solar cells where an exciton forms or dissociates. Understanding about dominating factors determining the intermolecular assembly and charge carrier exchange processes are highly anticipated for the establishment of smart design strategies of practically efficient devices. Molecular heterojunctions built on single crystal organic semiconductors provide well-ordered model systems disentangling complex intermolecular contacts in real devices. Moreover, the p-n junctions of highly ordered molecular assembly lead to the enhancement of the mobility of charge carriers and excitons through the inter-molecular delocalization of the electronic states, which potentially opens a new route for efficient optoelectronic applications of molecular semiconductors. In this contribution, crystallographic and electronic structures of well-ordered molecular semiconductor homo- and hetero-epitaxial junctions are overviewed. One representative system is a “complementary” p-n junction of perfluoropentacene (C22F14) crystalline ad-layers formed on the single crystal pentacene (C22H14) [1]. Grazing-incidence X-ray diffraction (GIXD) analyses revealed hetero-epitaxial growth of perfluoropentacene in a uniform crystallographic orientation with respect to the surface lattice of the single crystal pentacene. The energy-momentum dispersions of inter-molecular electronic bands were successfully demonstrated by angle-resolved photoelectron spectroscopy (ARPES) for the hetero-epitaxial perfluoropentacene as well as for the single crystal pentacene, which strongly suggests realization of the delocalization of electrons and holes across this well-ordered molecular p-n junction. To further improve the crystallinity of the epitaxial molecular heterojunctions, the authors’ group proposed a new concept of “quasi-homoepitaxial organic semiconductor junctions”, at which a molecular species with nearly identical in-plane lattice constants to those of the substrate molecular single crystal surface is stacked [2]. Actually, quasi-homoepitaxial crystallites of bis(trifluoromethyl)dimethylrubrene was revealed to form highly-ordered interface of much improved mean crystallite size on the single crystal surface of (unsubstituted) rubrene by means of high-resolution GIXD. The electronic structures exhibiting spontaneous electron transfer at this inter-molecular contact and possible opto-electronic applications of this quasi-homoepitaxial junction are also discussed in this presentation. This contribution is supported by Grant-in Aids for Transformative Research Areas (A) “Dynamic Exciton: Emerging Science and Innovation” (JSPS-KAKENHI Grant Number JP21H05405). [1] Y. Nakayama, et al., J. Phys. Chem. Lett. 10 (2019) 1312. [2] K. Takahashi, et al., J. Phys. Chem. Lett. 12 (2021) 11430.

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Xu, F. J., and B. Shen. "Progress in high crystalline quality AlN grown on sapphire for high-efficiency deep ultraviolet light-emitting diodes." Japanese Journal of Applied Physics 61, no. 4 (March 23, 2022): 040502. http://dx.doi.org/10.35848/1347-4065/ac3774.

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Abstract AlGaN with a high Al fraction and low-dimensional structure is an important material for deep ultraviolet (DUV) optoelectronic devices. However, due to a lack of high-quality and low-cost homogeneous AlN substrates, AlN is mainly prepared by heteroepitaxy on sapphire with a large lattice mismatch. The resulting defect density and residual stress in AlN films become a bottleneck for enhancing the performance of AlGaN-based DUV light-emitting devices. In this paper, the research advances in epitaxial growth and threading dislocation (TD) control of AlN on sapphire substrates at Peking University are described, including decreasing the tilt of AlN grains by nitridation pretreatment of sapphire, forming TD loops by growth mode alternations, bending and terminating TDs at the sidewall of voids by an image force on nano-patterned sapphire substrates, promoting the climbing and meeting of TDs by extrinsic supersaturated vacancies, etc. Based on high-quality AlN with a TD density of ∼108 cm−2, 276 nm DUV light-emitting diodes are fabricated with a light output power of 17.3 mW at an injection current of 100 mA.

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Yao, Yu, Dandan Sang, Susu Duan, Qinglin Wang, and Cailong Liu. "Review on the Properties of Boron-Doped Diamond and One-Dimensional-Metal-Oxide Based P-N Heterojunction." Molecules 26, no. 1 (December 25, 2020): 71. http://dx.doi.org/10.3390/molecules26010071.

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This review is mainly focused on the optoelectronic properties of diamond-based one-dimensional-metal-oxide heterojunction. First, we briefly introduce the research progress on one-dimensional (1D)-metal-oxide heterojunctions and the features of the p-type boron-doped diamond (BDD) film; then, we discuss the use of three oxide types (ZnO, TiO2 and WO3) in diamond-based-1D-metal-oxide heterojunctions, including fabrication, epitaxial growth, photocatalytic properties, electrical transport behavior and negative differential resistance behavior, especially at higher temperatures. Finally, we discuss the challenges and future trends in this research area. The discussed results of about 10 years’ research on high-performance diamond-based heterojunctions will contribute to the further development of photoelectric nano-devices for high-temperature and high-power applications.

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48

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, and 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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Dietz, Nikolaus, and Klaus J. Bachmann. "Real-Time Monitoring of Epitaxial Processes by Parallel-Polarized Reflectance Spectroscopy." MRS Bulletin 20, no. 5 (May 1995): 49–55. http://dx.doi.org/10.1557/s0883769400044894.

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The engineering of advanced micro-electronic circuits, optoelectronic devices, and integrated optical circuits requires precise control of the lateral dimensions and thicknesses of device features and of the stoichiometry and doping of epitaxial semiconductor regions. This is preferably achieved by real-time monitoring and control of the individual deposition and etching processes that constitute the processing sequence. The use of optical probe techniques for the real-time monitoring of etching and/or growth processes is favored because of their nondestructive character and their potential use in real-time feedback control. Some of these methods are ideal in monitoring the overall growth process and/or substrate temperature in industrial applications, requiring low cost and maintenance. For example, in situ reflectance-spectroscopy methods, such as dynamic optical reflectivity (DOS), spectral-resolved normal incidence reflectance spectroscopy (MRS), or pyrometric interferometry (PI), are successfully applied to various deposition processes and provide information on both the growth rate and the composition of the deposits. However, small changes in the reflectance (because of chemical interactions at the surface of the films with the reactants supplied from the vapor phase) are of the order of 10−3 to 10−4 and are hardly observable with normal-incidence reflectance techniques because of the high reflectivity of substrate/film interface, which is typically of the order of 40%–60% for many semiconductors.In order to increase the sensitivity to surface- and interface-related growth properties, alternative optical-observation methods such as reflectance difference spectroscopy (RDS), surface photoabsorption (SPA), and spectral ellipsometry (SE) have been developed.

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Ermolaev, Georgy A., Marwa A. El-Sayed, Dmitry I. Yakubovsky, Kirill V. Voronin, Roman I. Romanov, Mikhail K. Tatmyshevskiy, Natalia V. Doroshina, et al. "Optical Constants and Structural Properties of Epitaxial MoS2 Monolayers." Nanomaterials 11, no. 6 (May 27, 2021): 1411. http://dx.doi.org/10.3390/nano11061411.

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Two-dimensional layers of transition-metal dichalcogenides (TMDs) have been widely studied owing to their exciting potential for applications in advanced electronic and optoelectronic devices. Typically, monolayers of TMDs are produced either by mechanical exfoliation or chemical vapor deposition (CVD). While the former produces high-quality flakes with a size limited to a few micrometers, the latter gives large-area layers but with a nonuniform surface resulting from multiple defects and randomly oriented domains. The use of epitaxy growth can produce continuous, crystalline and uniform films with fewer defects. Here, we present a comprehensive study of the optical and structural properties of a single layer of MoS2 synthesized by molecular beam epitaxy (MBE) on a sapphire substrate. For optical characterization, we performed spectroscopic ellipsometry over a broad spectral range (from 250 to 1700 nm) under variable incident angles. The structural quality was assessed by optical microscopy, atomic force microscopy, scanning electron microscopy, and Raman spectroscopy through which we were able to confirm that our sample contains a single-atomic layer of MoS2 with a low number of defects. Raman and photoluminescence spectroscopies revealed that MBE-synthesized MoS2 layers exhibit a two-times higher quantum yield of photoluminescence along with lower photobleaching compared to CVD-grown MoS2, thus making it an attractive candidate for photonic applications.

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Journal articles on the topic 'Ga2O3 epitaxial growth and optoelectronic devices'

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