Normally-OFF AlGaN/GaN MIS-HEMTs with Low R_ONand V_thHysteresis by Functioning In-situ SiN_xin Regrowth Process

Normally-off AlGaN/GaN MIS-HEMTs with a high threshold voltage ( text{V}-{text {th}} ) more than 2.5 V and a low on- resistance of 5.5Omega cdot mm have been achieved by an improved regrowth technique with in-situ SiNx passivation. A thin-barrier heterojunction was used to decrease the two-dimensional electron gas (2DEG) underneath the gate, then regrown Al0.2Ga0.8N and in-situ SiNx were applied to recover 2DEG at the access regions and reduce contact resistance. The O3-based Al2O3 and HfO2 were employed to cover the recessed-gate with low channel sheet resistances by atomic layer deposition. The other hybrid MIS-HEMT with in-situ SiNx gate interlayer also enabled a normally-off operation with a text{V}-{text {th}} hysteresis lower than 30 mV. The damage-free recessed-gate structures with in- situ SiNx as passivation and gate dielectric contribute to reducing surface scattering and interface states, resulting in a high text{V}-{text {th}} uniformity and channel mobility, low on- resistance andth hysteresis in normally-off GaN-based MIS-HEMTs.