Under-gate defect formation in Ni-gate AlGaN/GaN high electron mobility transistors

AlGaN/GaN high electron mobility transistors (HEMTs) represent a rapidly maturing technology plagued by reliability issues which are not well understood. One such issue is the relationship between gate leakage and the formation of reaction-based defects at the interface between the gate metal and the underlying epitaxial semiconductor layers. Here, the combination of chemical etching-based deprocessing and top-down scanning electron microscopy (SEM) to identify and quantify defects formed between the gate and the epitaxial layers of HEMTs with Ni gates is presented. This approach is used to demonstrate a direct relationship between gate leakage current density during off-state stressing and the percentage of gate contact area consumed by reaction-based defects in HEMTs with 100 nm and 1.0 μm gate lengths.