Critical voltage for electrical reliability of GaN high electron mobility transistors on Si substrate

We have evaluated the electrical reliability of GaN HEMTs on Si by carrying out V_DS = 0 V step-stress experiments. We have found that these devices show a degradation pattern that is very similar to that of devices on SiC with a critical voltage at which a sudden degradation of the gate current takes place. In general, devices on Si have a relatively high critical voltage although its distribution on a wafer is fairly broad even on a short-range scale.