InAlAs/InGaAs MHEMT degradation during DC and thermal stressing

Reliability studies of InAlAs/InGaAs metamorphic high electron mobility transistors (MHEMTs) grown on GaAs substrates for high frequency/power applications are reported. The MHEMTs were stressed at a drain voltage of 3 V for 36 hrs, as well as undergoing a thermal storage test at 250°C for 48 hrs. Under both stress conditions, the drain current density decreased about 12.5%. The gate current, however, increased more after the thermal storage as opposed to DC bias. The main degradation mechanism during thermal storage was reaction of the Ohmic contact with the underlying semiconductor. Transmission electron microscopy verified that gate sinking occurred in devices that underwent DC bias stressing.