Current collapse and reliability mechanisms in GaN HEMTs

Current collapse and performance degradation effects remain the most serious problem in short channel GaN HEMTs with operating frequencies above 20 GHz and aggressive designs for achieving highest power levels (exceeding 6-8 W/mm). Although for lower frequency operation, significant progress in mitigating these effects has been achieved, this approach is not applicable for ultra high frequency, higher performance devices. To facilitate the development of such advanced devices, the authors propose novel model applicable to short (down to sub-100 nm) channel devices operating in high power regime. This novel model accounts for three different degradation mechanisms related to (a) current collapse, (b) gate leakage current degradation and (c) structural damage caused by high electric fields.