Normally-OFF AlGaN/GaN MIS-HEMTs With Low RON and Vth Hysteresis by Functioning In-situ SiNx in Regrowth Process

Abstract

Normally-off AlGaN/GaN MIS-HEMTs with a high threshold voltage (<inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {th}}$ </tex-math></inline-formula>) more than 2.5 V and a low on- resistance of <inline-formula> <tex-math notation="LaTeX">$5.5\Omega \cdot $ </tex-math></inline-formula>mm have been achieved by an improved regrowth technique with <i>in-situ</i> SiN_<i>x</i> passivation. A thin-barrier heterojunction was used to decrease the two-dimensional electron gas (2DEG) underneath the gate, then regrown Al_0.2Ga_0.8N and <i>in-situ</i> SiN_<i>x</i> 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 <i>in-situ</i> SiN_<i>x</i> gate interlayer also enabled a normally-off operation with a <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {th}}$ </tex-math></inline-formula> hysteresis lower than 30 mV. The damage-free recessed-gate structures with in- situ SiN_<i>x</i> as passivation and gate dielectric contribute to reducing surface scattering and interface states, resulting in a high <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {th}}$ </tex-math></inline-formula> uniformity and channel mobility, low on- resistance and_th hysteresis in normally-off GaN-based MIS-HEMTs.