Quasi-Normally-Off AlGaN/GaN HEMTs With SiNₓ Stress Liner and Comb Gate for Power Electronics Applications

Recess processes for the fabrication of normally-off GaN HEMTs generally compromise devices' on-state performance. In this work, recess-free quasi-normally-off GaN HEMTs with a threshold voltage of 0.24 V is realized by local control of two-dimensional electron gas (2DEG) density. The devices feature a 0.1 μm gate length, SiN
_x
stress liner, and comb gate. SiN
_x
liner can provide significant stress to AlGaN/GaN heterostructure in the scaled gate region. The additional stress translates to the additional electric field and depletes the 2DEG in the gate region. As a result, the quasi-normally-off operation is achieved. Furthermore, the comb gate structure is introduced to suppress the short channel effects, supported by TCAD simulation. The quasi-normally-off devices' excellent on-state performances are benchmarked against the normally-off devices reported recently and a p-GaN HEMT purchased from a commercial foundry. The results support strain engineering as a promising technique to pursue the normally-off operation of GaN HEMTs.