High temperature on- and off-state stress of GaN-on-Si HEMTs with in-situ Si3N4 cap layer

In this work the stability of Gallium Nitride based high electron mobility transistors grown on 4-in Si substrate (GaN-on-Si HEMTs) were tested both in off-state at high drain voltage (200 V) and in on-state at large gate voltage (+2 V) with low drain bias (5 V). In each stress experiment the ambient temperature was fixed at 200°C. Remarkably, despite the considerably large drain voltage used in the off-state stress on only 5 μm gate-drain spaced transistors, negligible signs of degradation were observed after more than 350 hours of testing. Similar results were obtained after the on-state stress. In fact, only small degradation signs were reported in spite of the large gate current and high junction temperature the devices have to withstand during the on-state stress. These results show the robustness of these devices to operate under high electric field conditions, high temperature and to withstand also a large gate current for considerable time.