MSE Colloquium: Zhenqiang Ma, Lattice-mismatched heterostructures as a solution to the major technical challenges faced in WBG and UWBG semiconductors

Dr. Zhenqiang Ma

Lynn H. Matthias Professor in Engineering & Vilas Distinguished Achievement Professor
Dept. of Electrical and Computer Engineering
University of Wisconsin, Madison

Abstract

Wide bandgap (WBG) and ultrawide bandgap (UWBG) semiconductors are attractive semiconductors that can enable high-voltage, high-frequency, and high power-density operations due to their wide bandgap, high breakdown electrical field strength, and high charge carrier mobilities and drift velocities. However, each bears with it some inherent disadvantages that cannot be solved based on the present understanding of solid-state physics. One of these disadvantages commonly faced by all the WBG (GaN, SiC) and UWBG (Al(Ga)N, B(Al)N, b-Ga₂O₃ and diamond) semiconductors is the asymmetric doping effectiveness. In other words, these attractive semiconductors can only be effectively doped into either n-type or p-type, and the other doping type is very poor. This severely limits the effective use of these semiconductors. Various approaches have been attempted to solve the doping deficiency issues but with limited practical implications.

In this talk, the speaker will introduce the concept of semiconductor grafting that was invented about a decade ago based on quantum tunneling principles. The grafting approach enables two semiconductors with arbitrary lattice constants/crystal structures to be intimately connected without disturbing the lattice structures of either semiconductor, forming an abrupt hetero interface with a very low interface trap density and therefore resulting in minimum charge carrier recombination at the interface. The epitaxy-like arbitrary-lattice (i.e, lattice mismatched) heterogeneous heterostructures can be exploited in the same way with conventional lattice-matched epitaxially grown heterostructures, which in turn, is expected to address many everlasting challenges faced in WBG and UWBG semiconductors that were not solvable with epitaxy or wafer bonding. WBG and UWBG bipolar devices, including diodes, heterojunction bipolar transistors (HBT), etc. enabled by grafting will be described in the talk followed by a perspective discussion.

Bio

Zhenqiang (Jack) Ma is a Lynn H. Matthias Professor in Engineering and a Vilas Distinguished Achievement Professor in the Department of Electrical and Computer Engineering at the University of Wisconsin-Madison. He received his Ph.D. degree in electrical engineering from the University of Michigan-Ann Arbor in 2001. Before he joined academia, he worked in the semiconductor industry for a year. His present research interests focus on the physics, materials, and applications to all possible types of devices of lattice-mismatched heterostructures based on 3D semiconductor materials. He has been actively working on microwave flexible electronics since 2005. In collaboration with biomedical engineering faculty and medical school physicians, he is investigating micro-structured scaffolds for human stem cell-based vision restoration. He has published over 550 papers. He is a fellow of AAAS, AIMBE, APS, IEEE, NAI, OSA, and SPIE.

Zoom Meeting

https://osu.zoom.us/j/94109057957?pwd=N1A2bjBZeDdBM2x6VXFaMXhZdGQ3dz09

Meeting ID: 941 0905 7957

Password: 126701