SCALE Defects and Radiation Interactions in Wide Bandgap Semiconductors

Professor Aris Christou of the University of Maryland presentation at the Vanderbilt Seminar Series.

Wide‑bandgap semiconductors such as gallium nitride (GaN) and ultra‑wide‑bandgap materials like diamond enable power‑electronics devices that operate at high voltage, high current, and high frequency. Understanding how crystalline defects and external radiation fields interact with the two‑dimensional electron gas in these devices is essential for reliable operation in demanding applications, including advanced magnetic‑resonance imaging systems and space‑borne power converters. The resource therefore concentrates on the defect physics and radiation response of GaN power transistors while also referencing comparative work on diamond.
The presentation examines the relationship between dislocation density, epitaxial thickness, and the critical electric field that determines breakdown voltage in vertical and lateral GaN devices. High‑field TCAD simulations are coupled with deep‑level transient spectroscopy (DLTS), capacitance‑voltage (C‑V) profiling, pulsed I‑V, and transient current measurements to locate bulk traps, surface states, and buffer‑layer defects. Frequency‑dependent current collapse, gate‑leakage enhancement, and hot‑electron injection under intense radiation are linked to trap‑assisted tunneling and piezoelectric relaxation. Radiation‑induced phenomena such as single‑event upset, burnout, gate rupture, and total‑dose effects are quantified through gamma‑irradiation experiments that reveal carrier‑removal thresholds around 10¹⁴ rad and progressive threshold‑voltage shifts up to tens of kilorads.