Thermal Stability and Failure Mechanism of Schottky Gate AlGaN/GaN HEMTs

This paper investigates the electrothermal stability and the predominant defect mechanism of a Schottky gate AlGaN/GaN HEMT. Calibrated 3-D electrothermal simulations are performed using a simple semiempirical dc model, which is verified against high-temperature measurements up to 440°C. To determine the thermal limits of the safe operating area, measurements up to destruction are conducted at different operating points. The predominant failure mechanism is identified to be hot-spot formation and subsequent thermal runaway, induced by large drain-gate leakage currents that occur at high temperatures. The simulation results and the high temperature measurements confirm the observed failure patterns.