Effects of Charge Generation and Trapping on the X-ray Response of Strained AlGaN/GaN HEMTs.

The piezoelectric properties of GaN enable it to sense mechanical strain. Effects of mechanical strain on device electrical response have been investigated in AlGaN/GaN HEMTs irradiated with ~10-keV X-rays. Radiation-induced charge trapping in these GaN-based HEMTs is attributed to fast-annealing donor-like defects, which are most likely O N impurities. Similar defects lead to threshold-voltage shifts, transconductance degradation, and enhanced low-frequency noise in AlGaN/GaN HEMTs. The amount of threshold-voltage variation induced by externally applied tensile stress decreases during irradiation exposure by as much as ~75% due to screening effects associated with charge generation, transport, and trapping.