Degradation of GaN High Electron Mobility Transistors under high-power and high-temperature stress

Abstract

GaN HEMTs (High Electron Mobility Transistors) are promising candidates for high power and high frequency applications but their reliability needs to be established before their wide deployment can be realized. In this thesis, degradation mechanisms of GaN HEMTs under high-power and high-temperature stress have been studied. A novel technique to extract activation energy of degradation rate from measurements on a single device has been proposed. High-power and high-temperature stress has revealed two sequential degradation mechanisms where the gate current degrades first and saturates only after which the drain current shows significant degradation. A study of the semiconductor surface of delaminated degraded devices shows formation of grooves and pits at the gate edge on the drain side. Electrical degradation is shown to directly correlate with structural degradation. Also, higher junction temperature is shown to results in more severe structural degradation.