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Research

III-Nitride Electronics Devices

We are working on making the next generation of III-Nitride electronic devices for applications related to communications, energy efficient power electronics, and extreme-environment logic. We have a range of projects that focus on realizing high-performance GaN devices by harnessing unique transport, heterostructure, and polarization phenomena in these materials. Ongoing projects include ultra-wide band gap high composition AlGaN-channel devices for high frequency applications, graded channel devices for microwave linearity, vertical high voltage GaN-based PN diodes, GaN-based logic, and Gallium Nitride HEMTs for power switching applications.

Recent publications and presentations:

Publications: 

1. Towhidur Razzak, Seongmo Hwang, Antwon Coleman, Hao Xue, Shahadat H. Sohel, Sanyam Bajaj, Yuewei Zhang, Wu Lu, Asif Khan, and Siddharth Rajan,  "Design of compositionally graded contact layers for MOCVD grown high Al-content AIGaN transistors" Applied Physics Letters 115 (4), 043502 (2019)

2. Hao Xue, Choong Hee Lee, Kamal Hussian, Towhidur Razzak, Mamun Abdullah, Zhanbo Xia, Shahadat Hasan Sohel, Asif Khan, Siddharth Rajan, and Wu Lu, "AI0.75Ga0.25N/AI0.6Ga0.4N heterojunction field effect transistor with fT of 40 GHz" Applied Physics Express 12 (6), 066502 (2019)

3. Shahadat H Sohel, Andy Xie, Edward Beam, Hao Xue, Towhidur Razzak, Sanyam Bajaj, Yu Cao, Cathy Lee, Wu Lu, and Siddharth Rajan,  IEEE Electron Device Letters 40 (4), 522 (2019)

4. Shahadat H Sohel, Andy Xie, Edward Beam, Hao Xue, Jason A Roussos, Towhidur Razzak, Sanyam Bajaj, Yu Cao, David J Meyer, and Wu Lu, "Polarization egineering of AIGaN/GaN HEMT with graded InGaN sub-channel for high-linearity X-band applications" IEEE Electron Device Letters 39 (12), 1884 (2018)

5. Towhidur Razzak, Seongmo Hwang, Antwon Coleman, Sanyam Bajaj, Hao Xue, Yuewei Zhang, Zane Jamal-Eddine, Shahadat H. Sohel, Wu Lu, Asif Khan and Siddharth Rajan,  "RF operation in graded AIxGa1-xN (x=0.65 to 0.82) channel transistors" Electronics Letters 54 (23), 1351 (2018)

Presentations: 

1. Shahadat H. Sohel, Andy Xie, Edward Beam, Hao Xue, Towhidur Razzak, Sanyam Bajaj, Yu Cao, Wu Lu, Siddharth Rajan, “High Linearity Graded AlGaN Channel Field Effect Transistors with Epitaxial Passivation,” 13th International Conference on Nitride Semiconductors (ICNS-13), July 7-12, 2019, Bellevue, Washington

2. Shahadat H. Sohel, Mohammad Wahidur Rahman, Andy Xie, Edward Beam, Yongjie Cui, Hao Xue, Towhidur Razzak, Sanyam Bajaj, Yu Cao, Wu Lu, Siddharth Rajan, “LPCVD passivation for High Linearity Graded AlGaN Channel Field Effect Transistors with improved dispersion,” 61st Electronic Materials Conference (EMC), June 26-28, 2019, University of Michigan, Ann Arbor, MI

3. Towhidur Razzak, Mohammad Kamal Hossain, Hao Xue, Choong Hee Lee, Zhanbo Xia, Shahadat Hasan Sohel, Sanyam Bajaj, Wu Lu, Asif Khan, Siddharth Rajan, “High Al-composition AlxGa1-xN Channel Transistors for Next Generation RF Applications” WOCSEMMAD (Workshop on Compound Semiconductor Materials and Devices), Feb 17-20, 2019, Jacksonville Beach, Florida

 

III-Nitride Optoelectronics

We are investigating next-generation GaN and AlGaN-based optoelectronics using novel concepts such as interband tunnel junctions, multiple active region emitters, and polarization engineering. Current active projects are focused an achieving tunneling-based cascaded LEDs, and ultraviolet UV LEDs using AlGaN-based tunnel junctions.

Recent publications and presentations

Publications:

1. Zhang, Y., Krishnamoorthy, S., Johnson, J.M., Akyol, F., Allerman, A., Moseley, M.W., Armstrong, A., Hwang, J. and Rajan, S., 2015. Interband tunneling for hole injection in III-nitride ultraviolet emitters. Applied Physics Letters, 106(14), p.141103.

2. Zhang, Y., Krishnamoorthy, S., Akyol, F., Allerman, A.A., Moseley, M.W., Armstrong, A.M. and Rajan, S., 2016. Design and demonstration of ultra-wide bandgap AlGaN tunnel junctions. Applied Physics Letters, 109(12), p.121102.

3. Akyol, F., Krishnamoorthy, S., Zhang, Y. and Rajan, S., 2015. GaN-based three-junction cascaded light-emitting diode with low-resistance InGaN tunnel junctions. Applied Physics Express, 8(8), p.082103.

4. Krishnamoorthy, S., Nath, D.N., Akyol, F., Park, P.S., Esposto, M. and Rajan, S., 2010. Polarization-engineered GaN/InGaN/GaN tunnel diodes. Applied Physics Letters, 97(20), p.203502.

 

Gallium Oxide Materials and Devices

Beta Gallium Oxide is an exciting material with a large band gap (4.7 eV) that makes it promising for high power electronics applications. Our group investigates the material growth, device design, and electronic properties of these materials. Ongoing projects related to this include study of molecular beam epitaxy techniques to realize Ga2O3 and (Al,Ga)2O3 films, the electronic properties such as transport, doping, and breakdown, radiation effects in Ga2O3, properties of alloys and heterostructures, and demonstration of high-performance device architectures for vertical and lateral devices.

Recent publications and presentations


Publications:

1.Krishnamoorthy, S., Xia, Z., Joishi, C., Zhang, Y., McGlone, J., Johnson, J., Brenner, M., Arehart, A.R., Hwang, J., Lodha, S. and Rajan, S., 2017. Modulation-doped β-(Al0. 2Ga0. 8) 2O3/Ga2O3 field-effect transistor. Applied Physics Letters, 111(2), p.023502.

2.Krishnamoorthy, S., Xia, Z., Bajaj, S., Brenner, M. and Rajan, S., 2017. Delta-doped β-gallium oxide field-effect transistor. Applied Physics Express, 10(5), p.051102.

3. Zhang, Y., Neal, A., Xia, Z., Joishi, C., Johnson, J.M., Zheng, Y., Bajaj, S., Brenner, M., Dorsey, D., Chabak, K. and Jessen, G., 2018. Demonstration of high mobility and quantum transport in modulation-doped β-(AlxGa1-x) 2O3/Ga2O3 heterostructures. Applied Physics Letters, 112(17), p.173502.

Presentations:

1. Nidhin Kurian Kalarickal, Zhanbo Xia, Joe McGlone, Yuewei Zhang, Wyatt Moore, Aaron R. Arehart, Steven A. Ringel, Siddharth Rajan, High Electron Density β-(Al0.23Ga0.77)2O3/Ga2O3 Modulation Doped Heterostructures,” 61st Electronic Materials Conference (EMC), June 26-28, 2019, University of Michigan, Ann Arbor, MI

 

Perovskite Oxide-Based Semiconductor Devices

Perovskite oxides are a family of materials with unique properties that are not found in conventional semiconductors. Our group is studying various perovskite oxides such as BaSnO3, SrTiO3, BaTiO3 and their heterostructures. Current active projects include investigations of the electronic properties of (Sr,Ba)SnO3, study of metal-insulator phenomena at oxide interfaces and device applications, and the use of perovskite materials for high power and high frequency field effect transistors.

Recent publications and presentations

Publications:

1. Zhanbo Xia, Caiyu Wang, Nidhin Kurian Kalarickal, Susanne Stemmer, Siddharth Rajan, “Design of Transistors Using High-Permittivity Materials”, IEEE Transactions on Electron Devices 66(2), 896-900 (2019).

2. Hareesh Chandrasekar, Junao Cheng, Tianshi Wang, Zhanbo Xia, Nicholas G. Combs, Christopher R. Freeze, Patrick B. Marshall, Joe McGlone, Aaron Arehart, Steven Ringel, Anderson Janotti, Susanne Stemmer, Wu Lu and Siddharth Rajan, “Velocity Saturation in La-doped BaSnO3 Thin Films”, accepted at Applied Physics Letters (2019).

3. M Boucherit, O Shoron, CA Jackson, TA Cain, MLC Buffon, C Polchinski, S Stemmer, S Rajan, “Modulation of over 1014 cm−2 electrons in SrTiO3/GdTiO3 heterostructures”, Applied Physics Letters 104(18), 182904 (2014).

Presentations:

1. Hao Yang, Junao Cheng, Caiyu Wang, Christopher Freeze, Omor Shoron, Nicholas G. Combs, Wangzhou Wu,Susanne Stemmer, Siddharth Rajan and Wu Lu, “Enhancement Mode Perovskite Oxide BaSnO3 MOSFETs with Current On/Off Ratio of 108”, 61st Electronic Materials Conference (EMC), June 26-28, 2019, University of Michigan, Ann Arbor, MI.

2. Hareesh Chandrasekar, Junao Cheng, Nicholas G Combs, Patrick B Marshall, Susanne Stemmer, Wu Lu and Siddharth Rajan, “Velocity Saturation in BaSnO3 Thin Films”, 61st Electronic Materials Conference (EMC), June 26-28, 2019, University of Michigan, Ann Arbor, MI.

3. Junao Cheng, Caiyu Wang, Nidhin Kurian Kalarickal, Christopher Freeze, Omor Shoron, Nick Combs, Zhanbo Xia, Hao Xue, Susanne Stemmer, Siddharth Rajan and Wu Lu, “High-Current Perovskite Oxide BaTiO3/BaSnO3 Heterostructure Transistors”, 2018 Lester Eastman Conference on High-Performance Devices, August 12-14, 2018, Columbus, OH.