GaN-on-Si HEMT stress under high electric field condition

Nowadays, GaN‐on‐Si HEMTs (High Electron Mobility transistors) are receiving a lot of attention thanks to their impressive performance in terms of high current and voltage capabilities combined with a low production cost. Since the technology has matured, the reliability aspects have been initially investigated in order to prove the performances of these devices in the long term. In this work GaN‐on‐Si HEMTs were electrically stressed in pinched off condition while high voltages were applied on the drain side (high electric field condition). Transistors with and without in‐situ Si3N4 layer underneath the gate were tested, as well as a transistor with 1 μm field plate on each side, due to a T shaped gate. Both type of devices with and without Si3N4 under the gate showed the same failure mode: a sudden increase of the gate and drain leakage current. This excludes, in principle, the role of Si3N4 layer on the degradation mechanism involved. Possible explanations about the failure mechanism are compared and discussed. Finally, a preliminary test on the T‐shape gate technology showed no degradation after more than 500 hours under high electric field condition of stress, which include 282 hours in pinched off condition with the drain voltage fixed as high as 60 V. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)