Quasi-Normally-Off AlGaN/GaN HEMTs with Strained Comb Gate for Power Electronics Applications

The quasi-normally-off operation of AlGaN/GaN HEMTs was realized using strain engineering. The dual-layer silicon nitride (SiNx) stressors applied compression to the gate region in devices, and the introduced compression translated to piezoelectric polarization charges and hence, increased the threshold voltage of devices. The devices with dual-layer stressors showed quasi-normally-off characteristics and the threshold voltage of 0.17 V. Besides, the comb-gate structure was introduced to suppress the short channel effects. The on-state performance of the comb-gate devices, including on-resistance
$(\pmb{R}_{\pmb{on}})$
and saturation current
$(\pmb{I}_{\pmb{d},\pmb{sat}})$
, was benchmarked against that of p-GaN gate HEMTs from a commercial foundry. The dual-layer stressor and comb-gate structure further improved the feasibility of strain engineering as a practical approach in the pursuit of the normally-off operation of AIGaN/GaN HEMTs in power electronics applications.