Reliability behavior of GaN HEMTs related to Au diffusion at the Schottky interface

Abstract

AbstractThe Schottky contact on GaN HEMT power devices is a key element for high power performance and its long term reliability behavior. Up to now such GaN devices are still suffering very often by a leakage current increase during operation resulting in deteriorated transistor behavior. One reason for this problem is owing to insufficiently stable Schottky contacts based on NiAu metalisation. We analysed GaN HEMTs with different aging behaviors by means of HR‐TEM and EDX investigations. It could be shown that on transistors with increasing leakage current Au was found directly on the Schottky interface which may be responsible for the increase of the leakage current. Furthermore, there are strong indications that such Au is diffusing via the gate foot side wall Ni‐SiN interface towards the Schottky barrier. It is proposed that an additional metallic diffusion barrier may solve this aging problem. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)