Article
Engineering, Electrical & Electronic
Filip Gucmann, Peter Nadazdy, Kristina Husekova, Edmund Dobrocka, Juraj Priesol, Fridrich Egyenes, Alexander Satka, Alica Rosova, Milan Tapajna
Summary: The thermal stability of undoped epitaxial α- and β-Ga2O3 thin films grown on sapphire substrates was investigated using high-temperature X-ray diffraction and room temperature cathodoluminescence. α-Ga2O3 layers showed good thermal stability up to 800 degrees C, while β-Ga2O3 layers remained stable even at 1100 degrees C. The cathodoluminescence spectra revealed distinctive emission bands associated with α- and β-Ga2O3, indicating their near band-edge emissions.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Engineering, Electrical & Electronic
Amit Kumar Singh, Saurabh Yadav, P. K. Kulriya, Y. S. Katharria
Summary: In this study, the annealing effects of sapphire substrate on beta-Ga2O3 thin films were investigated. The results showed that annealing improved the crystalline quality of the thin films and confirmed the presence of Ga-O bonds. The annealing temperature of the sapphire substrate influenced the film quality and the diffusion of aluminum atoms.
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
(2022)
Article
Engineering, Electrical & Electronic
Liangliang Guo, Suzhen Luan, Hongpeng Zhang, Lei Yuan, Yuming Zhang, Renxu Jia
Summary: In this article, planar beta-Ga2O3 junctionless transistors with/without unintentional doping (UID) buffer layer are investigated numerically. The study reveals a trade-off between threshold voltage (V-th) and device reliability in double-layer Ga2O3 MOSFETs, as a result of anomalous Fe out-diffusion. An adequate buffer layer is found to be beneficial to the pinch-off characteristic of beta-Ga2O3 planar MOSFETs. The study also proposes a novel triple-layer MOSFET with a low-doped beta-Ga2O3 surface layer to modulate V-th by adjusting the thickness and doping concentration of the surface layer, and discusses the effect of the lateral extension N+ region.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Physics, Applied
Ta-Shun Chou, Palvan Seyidov, Saud Bin Anooz, Raimund Grueneberg, Jana Rehm, Tran Thi Thuy Vi, Andreas Fiedler, Kornelius Tetzner, Zbigniew Galazka, Martin Albrecht, Andreas Popp
Summary: In this study, the development of unwanted parasitic particles in the MOVPE chamber during the growth of mu m level films is comprehensively investigated. The density of parasitic particles is observed to be significant at film thicknesses starting from >1.5 to 2 mu m. These particles induce structural defects, such as twin lamellae, which adversely affect the electrical properties of the grown film. The parasitic particles originate from parasitic reactions within the chamber triggered by the promoted gas-phase reactions during the growth process, and their density can be reduced by increasing total gas flow and reducing the showerhead distance to the susceptor. After minimizing the density of parasitic particles, film thicknesses up to 4 mu m have been achieved. RT Hall measurements reveal carrier mobilities of 160 cm(2)V(-1)s(-1) at carrier concentrations of 5.7 x 10(16) cm(-3).
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Ke Zeng, Rohith Soman, Zhengliang Bian, Seungbin Jeong, Srabanti Chowdhury
Summary: The lack of an effective current blocking layer in Ga2O3 has been a major barrier to achieving a vertical MOSFET. However, a selective diffusion doping technique utilizing magnesium-doped spin-on-glass has been used to form a current blocking layer, leading to the successful demonstration of a vertical Ga2O3 MOSFET for the first time.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Ray-Hua Horng, Dong-Sing Wuu, Po-Liang Liu, Apoorva Sood, Fu-Gow Tarntair, Yu-Hsuan Chen, Singh Jitendra Pratap, Ching -Lien Hsiao
Summary: In this study, monoclinic gallium oxide (beta-Ga2O3) epilayer was successfully grown on a sapphire substrate by MOCVD. Controlling the growth temperature, TEGa flow rate, and growth time improved the crystallization characteristics of the epilayers. However, it also increased the surface roughness of beta-Ga2O3 film. The growth mechanism and chemical reactions between TEGa and oxygen precursors were analyzed.
MATERIALS TODAY ADVANCES
(2022)
Article
Materials Science, Ceramics
Xiaokun Yang, Xuejian Du, Jie Liu, Rongrong Chen, Di Wang, Yong Le, Hongyan Zhu, Bo Feng, Jin Ma, Hongdi Xiao
Summary: Nanoporous GaN wafers fabricated by electrochemical etching were used as substrates to deposit Er-doped Ga2O3 epitaxial films, which showed excellent crystal quality and optoelectronic properties. The films have great potential for fabricating Ga2O3 optoelectronic devices.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Multidisciplinary
Kazimieras Badokas, Arunas Kadys, Dominykas Augulis, Juras Mickevicius, Ilja Ignatjev, Martynas Skapas, Benjaminas Sebeka, Giedrius Juska, Tadas Malinauskas
Summary: The remote epitaxy of GaN epilayers on GaN/sapphire templates using different types of graphene interlayers was studied. The quality and structure of the graphene interlayers and GaN epilayers were analyzed using various techniques. The successful exfoliation of GaN membrane was demonstrated.
Article
Materials Science, Coatings & Films
A. F. M. Anhar Uddin Bhuiyan, Zixuan Feng, Hsien-Lien Huang, Lingyu Meng, Jinwoo Hwang, Hongping Zhao
Summary: Epitaxial growth of kappa-phase Ga2O3 thin films on various substrates is investigated. Pure kappa-Ga2O3 films are successfully grown on specific substrates by tuning the growth parameters. The structural, surface morphological, and chemical properties of the films grown on different substrates are studied.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Article
Chemistry, Physical
Yuxin Deng, Ziqi Yang, Tongling Xu, Huaxing Jiang, Kar Wei Ng, Chao Liao, Danni Su, Yanli Pei, Zimin Chen, Gang Wang, Xing Lu
Summary: Due to the difficulty of p-type doping in beta-Ga2O3, the NiO/beta-Ga2O3 heterojunction is considered as a promising candidate for bipolar devices. In this study, the band alignment and electrical properties of NiO/beta-Ga2O3 heterojunctions with different beta-Ga2O3 orientations were comparatively studied. It was found that there is a type-II band alignment between NiO and beta-Ga2O3, and the valence band offsets and conduction band offsets vary with different substrate orientations. The influence of substrate orientations on the properties of NiO/beta-Ga2O3 heterojunctions is of great importance for the design and optimization of beta-Ga2O3-based heterojunction devices.
APPLIED SURFACE SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Mohi Uddin Jewel, Samiul Hasan, Scott R. Crittenden, Vitaliy Avrutin, Umit Ozgue, Hadis Morkoc, Iftikhar Ahmad
Summary: The growth of monoclinic phase-pure gallium oxide (beta-Ga2O3) layers was achieved by metal-organic chemical vapor deposition on sapphire and AlN templates, using SiOx as a phase stabilizer. The addition of SiOx resulted in improved surface quality and resistivity of the beta-Ga2O3 layers. X-ray diffraction and Raman spatial mapping confirmed the presence of a pure-monoclinic phase and higher tensile strain in the films with SiOx. Epitaxial growth of beta-Ga2O3 on the AlN template also led to significant changes in surface morphology.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Engineering, Electrical & Electronic
Chenyu Liu, Yibo Wang, Wenhui Xu, Xiaole Jia, Shuqi Huang, Yuewen Li, Bochang Li, Zhengdong Luo, Cizhe Fang, Yan Liu, Tiangui You, Xin Ou, Yue Hao, Genquan Han
Summary: We report on a unique positive bias stress (PBS) instability observed in the heterogeneous Ga2O3-on-SiC metal-oxide-semiconductor field-effect transistor (MOSFET). The presence of hydrogen in the Ga2O3 layer of the GaOSiC MOSFET leads to different shifts in threshold voltage (V-TH) and on-resistance (R-ON) under PBS compared to transistors on Ga2O3 bulk. The PBS initially causes a positive V-TH shift, but as the time increases, the shift becomes negative due to the generation of shallow donors and increased carrier density (n(e)) in the Ga2O3 channel.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Physics, Applied
Alexander Polyakov, Vladimir Nikolaev, Sergey Stepanov, Alexei Almaev, Alexei Pechnikov, Eugene Yakimov, Bogdan O. Kushnarev, Ivan Shchemerov, Mikhail Scheglov, Alexey Chernykh, Anton Vasilev, Anastasia Kochkova, Lyubov Guzilova, Stephen J. Pearton
Summary: The electrical and structural properties of alpha-Ga2O3 grown by HVPE are significantly influenced by the sapphire substrate orientation, and the use of alpha-Cr2O3 buffers has three major effects on it.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Byungsoo Kim, Seungju Kim, Tae Hyung Lee, Duyoung Yang, Dongyup Lee, Woonbae Sohn, Euijoon Yoon, Yongjo Park, Ho Won Jang
Summary: This study achieved highly enhanced photoelectrical performance of UVC PDs by implementing single-domain epitaxy on a hexagonal sapphire substrate. The 2D beta-Ga2O3 films exhibited a smooth surface and low concentration of point defects, enabling efficient charge separation. Additionally, a tailored anti-reflection coating was adopted to improve charge generation.
Article
Chemistry, Multidisciplinary
Yuwen Huang, Xiaoping Xie, Zeyulin Zhang, Peng Dong, Zhe Li, Dazheng Chen, Weidong Zhu, Shenglei Zhao, Qian Feng, Jincheng Zhang, Chunfu Zhang, Yue Hao
Summary: The use of p-type oxide as the current-blocking layer in the vertical heterojunction Ga2O3 MOSFET greatly improves device performance. By adjusting the doping concentration and thickness, the threshold voltage and breakdown voltage can be modified. Furthermore, other p-type oxides show promising performances as well.
APPLIED SCIENCES-BASEL
(2022)
Article
Chemistry, Multidisciplinary
Benedikt Hauer, Claire E. Marvinney, Martin Lewin, Nadeemullah A. Mahadik, Jennifer K. Hite, Nabil Bassim, Alexander J. Giles, Robert E. Stahlbush, Joshua D. Caldwell, Thomas Taubner
ADVANCED FUNCTIONAL MATERIALS
(2020)
Article
Physics, Applied
Marko J. Tadjer, Fikadu Alema, Andrei Osinsky, Michael A. Mastro, Neeraj Nepal, Jeffrey M. Woodward, Rachael L. Myers-Ward, Evan R. Glaser, Jaime A. Freitas, Alan G. Jacobs, James C. Gallagher, Alyssa L. Mock, Daniel J. Pennachio, Jenifer Hajzus, Mona Ebrish, Travis J. Anderson, Karl D. Hobart, Jennifer K. Hite, Charles R. Eddy Jr.
Summary: Gallium oxide as an ultra-wide bandgap semiconductor shows significant potential in advancing power electronic devices due to its high breakdown electric field and mature substrate technology. However, a key challenge remains in growing electronic-grade epitaxial layers at rates consistent with the thickness needed for high voltage technologies. This study reports on the characterization of epitaxial layers grown at relatively high rates, showing improved quality and potential for future high voltage power device technologies.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Physics, Applied
Minh Anh Phan Nguyen, Jennifer Hite, Michael A. Mastro, Mehran Kianinia, Milos Toth, Igor Aharonovich
Summary: This study investigates the nature of quantum emitters in GaN grown on samples with different growth orientations, revealing consistent formation of quantum emitters in Ga-polar regions. Findings shed light on the origins of these quantum emitters and demonstrate site-selective formation in GaN. Through various tests, the overall defectivity of Ga-polar GaN synthesized using a specific growth procedure is attributed to the formation of quantum emitters.
APPLIED PHYSICS LETTERS
(2021)
Article
Materials Science, Coatings & Films
Michael A. Mastro, Charles R. Eddy, Marko J. Tadjer, Jennifer K. Hite, Jihyun Kim, Stephen J. Pearton
Summary: Recent advancements in bulk crystal growth of beta-Ga2O3 have led to commercialization of large-area substrates and high-quality films on (010) substrates, revealing subnanometer-scale facets and larger ridges on the surface. Recommendations for standardizing substrates to control ridge formation have been proposed based on density function theory calculations.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2021)
Article
Engineering, Electrical & Electronic
James C. Gallagher, Travis J. Anderson, Andrew D. Koehler, Mona A. Ebrish, Geoffrey M. Foster, Michael A. Mastro, Jennifer K. Hite, Brendan P. Gunning, Robert J. Kaplar, Karl D. Hobart, Francis J. Kub
Summary: This work focuses on fabricating vertical p-i-n GaN diodes using Raman spectroscopy to monitor carrier concentration, discovering that the uniformity of the wafers affects device performance. Avoiding electron-donating defects in the wafers significantly improves rectification ratio and reduces reverse bias leakage current.
JOURNAL OF ELECTRONIC MATERIALS
(2021)
Article
Engineering, Electrical & Electronic
Mona A. Ebrish, Travis J. Anderson, Alan G. Jacobs, James C. Gallagher, Jennifer K. Hite, Michael A. Mastro, Boris N. Feigelson, Yekan Wang, Michael Liao, Mark Goorsky, Karl D. Hobart
Summary: This research examines the optimal conditions for Mg ion implantation and activation, finding that in situ epitaxial-grown AlN caps are more suitable for GaN activation annealing, and a high dose is needed at the surface to facilitate ohmic contact formation. This work provides valuable information for achieving an electrical activation of implanted Mg while maintaining the integrity of the crystalline structure of GaN.
JOURNAL OF ELECTRONIC MATERIALS
(2021)
Article
Materials Science, Coatings & Films
Clarence Y. Chan, Shunya Namiki, Jennifer K. Hite, Michael A. Mastro, Syed B. Qadri, Xiuling Li
Summary: Metal-assisted chemical etching is a plasma-free method that can produce high aspect ratio structures, with potential applications in electronic and optoelectronic devices. The method was successfully demonstrated with ordered micropillar arrays of homoepitaxial GaN, showing promising results in spatially resolved photoluminescence. This approach may also be extended to InGaN and AlGaN, offering a facile and scalable processing route for III-nitride based devices.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2021)
Article
Instruments & Instrumentation
Md Shafkat Bin Hoque, Yee Rui Koh, Kiumars Aryana, Eric R. Hoglund, Jeffrey L. Braun, David H. Olson, John T. Gaskins, Habib Ahmad, Mirza Mohammad Mahbube Elahi, Jennifer K. Hite, Zayd C. Leseman, W. Alan Doolittle, Patrick E. Hopkins
Summary: This study investigates the thermal conductivity of buried substrates using the optical pump-probe technique SSTR, providing guidance for future measurements. The steady-state nature of SSTR allows it to measure the thermal properties of buried substrates that are traditionally challenging to measure with transient pump-probe techniques.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Materials Science, Multidisciplinary
Yee Rui Koh, Md Shafkat Bin Hoque, Habib Ahmad, David H. Olson, Zeyu Liu, Jingjing Shi, Yekan Wang, Kenny Huynh, Eric R. Hoglund, Kiumars Aryana, James M. Howe, Mark S. Goorsky, Samuel Graham, Tengfei Luo, Jennifer K. Hite, W. Alan Doolittle, Patrick E. Hopkins
Summary: This study explores the thermal conductivity of homoepitaxial GaN films grown using different techniques, revealing that doped films exhibit significantly lower thermal conductivities. Defects and GaN/GaN interfaces limit thermal transport in unintentionally doped homoepitaxial GaN films.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Materials Science, Coatings & Films
Jeffrey M. Woodward, Samantha G. Rosenberg, David R. Boris, Michael J. Johnson, Scott G. Walton, Scooter D. Johnson, Zachary R. Robinson, Neeraj Nepal, Karl F. Ludwig Jr, Jennifer K. Hite, Charles R. Eddy Jr
Summary: Plasma-enhanced atomic layer deposition (PEALD) enables the epitaxial growth of ultrathin indium nitride (InN) films with reduced process temperatures and better control of layer thickness. The relationship between plasma properties and growth kinetics is crucial for optimizing growth parameters. In this study, in situ investigation using grazing incidence small-angle x-ray scattering (GISAXS) reveals that the production of nitrogen species in the plasma influences the growth mode, with high concentrations promoting island growth and low concentrations promoting layer-plus-island growth. The results demonstrate the potential to control the growth kinetics of epitaxial films during PEALD by manipulating specific plasma species generation regimes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Article
Materials Science, Multidisciplinary
Alan G. Jacobs, Joseph A. Spencer, Jennifer K. Hite, Karl D. Hobart, Travis J. Anderson, Boris N. Feigelson
Summary: Codoping of gallium nitride with magnesium and silicon or oxygen via ion implantation and symmetric multicycle rapid thermal annealing is demonstrated. The results show enhanced photoluminescence, especially with oxygen codoping. The addition of nitrogen helps to balance stoichiometry and suppress defect photoluminescence signals. These findings have important implications for device design and the future use of ion implantation.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Review
Crystallography
Jennifer K. Hite
Summary: This paper reviews the basic issues in homoepitaxial growth of III-nitrides for vertical device technology. It focuses on using MOCVD to grow GaN and explores the effects of native substrate characteristics on material quality and device performance. The review also includes theoretical understanding of dopants in AlN and BN for future expansion into these materials.
Article
Crystallography
Alan G. G. Jacobs, Boris N. N. Feigelson, Joseph A. A. Spencer, Marko J. J. Tadjer, Jennifer K. K. Hite, Karl D. D. Hobart, Travis J. J. Anderson
Summary: Selective area doping is crucial for modern devices. In this study, efficient silicon ion activation in GaN was achieved through symmetrical multicycle rapid thermal annealing. The activation efficiency and mobility improved with increasing annealing temperature. The results demonstrate efficient dopant activation with low unintentional doping, making it suitable for high-voltage, high-power devices. Additionally, high activation and mobility have been achieved with GaN on sapphire, which offers commercial potential due to its large-area and robust substrates.
Article
Microscopy
Andrew J. Winchester, Travis J. Anderson, Jennifer K. Hite, Randolph E. Elmquist, Sujitra Pookpanratana
Summary: Photoemission electron microscopy (PEEM) is a powerful tool for studying electronic properties. Traditionally, it was mainly used with synchrotron light sources, but recent advancements in solid-state lasers have allowed for the development of laboratory-based PEEMs using laser-based UV light. This study reports on the characteristics of a laser-based UV light source integrated with a PEEM instrument and highlights the improved image quality compared to conventional light sources.
Proceedings Paper
Engineering, Electrical & Electronic
Clarence Y. Chan, Shunya Namiki, Jennifer K. Hite, Xiuling Li
Summary: In this study, photo-enhanced metal-assisted chemical etching was demonstrated on homoepitaxial n-UaN on HVPE GaN substrates. The etch rate achieved was comparable to or better than using RIE, with no degradation in band-edge emission observed.
2021 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)
(2021)