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1. β-Gallium oxide power electronics

Author

Andrew J. Green, James Speck, Grace Xing, Peter Moens, Fredrik Allerstam, Krister Gumaelius, Thomas Neyer, Andrea Arias-Purdue, Vivek Mehrotra, Akito Kuramata, Kohei Sasaki, Shinya Watanabe, Kimiyoshi Koshi, John Blevins, Oliver Bierwagen, Sriram Krishnamoorthy, Kevin Leedy, Aaron R. Arehart, Adam T. Neal, Shin Mou, Steven A. Ringel, Avinash Kumar, Ankit Sharma, Krishnendu Ghosh, Uttam Singisetti, Wenshen Li, Kelson Chabak, Kyle Liddy, Ahmad Islam, Siddharth Rajan, Samuel Graham, Sukwon Choi, Zhe Cheng, and Masataka Higashiwaki

Subjects
Biotechnology, TP248.13-248.65, Physics, QC1-999
Abstract

Gallium Oxide has undergone rapid technological maturation over the last decade, pushing it to the forefront of ultra-wide band gap semiconductor technologies. Maximizing the potential for a new semiconductor system requires a concerted effort by the community to address technical barriers which limit performance. Due to the favorable intrinsic material properties of gallium oxide, namely, critical field strength, widely tunable conductivity, mobility, and melt-based bulk growth, the major targeted application space is power electronics where high performance is expected at low cost. This Roadmap presents the current state-of-the-art and future challenges in 15 different topics identified by a large number of people active within the gallium oxide research community. Addressing these challenges will enhance the state-of-the-art device performance and allow us to design efficient, high-power, commercially scalable microelectronic systems using the newest semiconductor platform.

Published
2022
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7. List of contributors

Author

Akhil Ajay, Nazmul Arefin, Francesco Bertazzi, John D. Bullough, Martin D.B. Charlton, Chi-Feng Chen, Tzung-Te Chen, Yuk Fai Cheung, Ching-Hsueh Chiu, Hoi Wai Choi, Pei-Ting Chou, Chun-Fan Dai, Carlo De Santi, Houqiang Fu, Han-Kuei Fu, Michele Goano, Hideki Hirayama, Ray-Hua Horng, Run Hu, C.-Y. Huang, JianJang Huang, Tadakazu Ikenaga, S.M. Islam, D. Jena, Matthew H. Kane, Yulia Kotsar, Richard Kotschenreuther, Hao-Chung Kuo, Chun-Feng Lai, Yu-Pin Lan, Wonseok Lee, Zhen-Yu Li, Chien-Chung Lin, Chia-Feng Lin, Da-Wei Lin, Xiaobing Luo, Zetao Ma, Koh Matsumoto, Gaudenzio Meneghesso, Matteo Meneghini, Akira Mishima, Eva Monroy, Guanxi Piao, V. Protasenko, Jae-Hyun Ryou, James Speck, Linas Svilainis, Toshiya Tabuchi, Alberto Tibaldi, Hiroki Tokunaga, Yuji Tomita, Akinori Ubukata, Marco Vallone, A. Verma, J. Verma, Giovanni Verzellesi, Chien-Ping Wang, Yuh-Renn Wu, Zhanchao Wu, Dong-Sing Wuu, Zhiguo Xia, Yoshiki Yano, Wen-Yung Yeh, Enrico Zanoni, Yuji Zhao, and Qiandong Zhuang

Published
2018
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8. Structural and electronic properties of Ga2O3-Al2O3 alloys

Author

Chris Van de Walle, James Speck, Joel Varley, Harty Peelaers, and Hartwin Peelaers

Subjects
010302 applied physics, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, Band gap, Alloy, 02 engineering and technology, Crystal structure, engineering.material, 021001 nanoscience & nanotechnology, 01 natural sciences, Lattice constant, Lattice (order), 0103 physical sciences, engineering, Density functional theory, 0210 nano-technology, Phase diagram, Monoclinic crystal system
Abstract

Ga2O3 is emerging as an important electronic material. Alloying with Al2O3 is a viable method to achieve carrier confinement, to increase the bandgap, or to modify the lattice parameters. However, the two materials have very different ground-state crystal structures (monoclinic β-gallia for Ga2O3 and corundum for Al2O3). Here, we use hybrid density functional theory calculations to assess the alloy stabilities and electronic properties of the alloys. We find that the monoclinic phase is the preferred structure for up to 71% Al incorporation, in close agreement with experimental phase diagrams, and that the ordered monoclinic AlGaO3 alloy is exceptionally stable. We also discuss bandgap bowing, lattice constants, and band offsets that can guide future synthesis and device design efforts.

Published
2018
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18. (Invited) Unraveling the Efficiency Limits of GaN-Based Emitters and the Surprising Connection to Electron Devices

Author

James Speck

Abstract

In this talk, we review our recent experiments designed to reveal the fundamental efficiency limits of GaN-based LEDs: (i) electroemission spectroscopy studies of InGaN-based LEDs with cesiated surfaces provide the first direct measurement of Auger electrons that result from an electron-electron-hole (eeh) Auger process. Auger-generated electrons survive transit through the p-GaN by transfer to a low lying side valley. The relationship between the observation of Auger electrons and the onset of droop provides compelling evidence that the internal Auger process is the dominant droop mechanisms [1]; (ii) related above gap photoemission studies on p-GaN with cesiated surfaces demonstrate a low level side conduction band valley (nominally referred to as “L”) ~0.9 eV above Γ [2]; (iii) atom probe tomography studies on InGaN-based LEDs demonstrate that the indium alloy follows a binomial distribution, as expected for a random alloy. 2D drift-diffusion simulations show that the alloy fluctuations are essential to explain the low turn-on voltages of InGaN-based LEDs [3]; (iv) vertical carrier transport studies on majority carrier analogs to LEDs, namely all n-type InGaN/GaN MQWs and GaN/AlGaN/GaN structures confirm the importance of natural alloy fluctuations in vertical transport [4,5]. [1] J. Iveland et al., Phys Rev. Lett. 110, 177406 (2013) [2] M. Piccardo et al., Phys. Rev. B, in press (2014) [3] Y.-R. Wu et al., Appl. Phys. Lett. 101, 083505 (2012) [4] D. Browne et al., in preparation (2014) [5] M. Fireman et al., in preparation (2014)

Published
2015
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21. Engineering of quantum barriers for efficient InGaN quantum well LEDs

Author

Yapparov, R., Lynsky, C., Chow, Y. C., Nakamura, S., Denbaars, S. P., James Speck, and Marcinkevičius, S.

Abstract

Ways to improve efficiency of high-power LEDs based on InGaN/(In)GaN multiple quantum wells are explored by studying interwell carrier transport and recombination. Best results are achieved for InGaN barriers with thin GaN or AlGaN interlayers.

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