Achieving 205 $\text{cm}^{2}\mathrm{V}^{-1}\mathrm{s}^{-1}$ Inversion Channel Mobility in 1.4 kV Vertical GaN-on-GaN MISFET with Nitride Gate Dielectric

We demonstrate a 1.4 $\text{kV}/2.0\ \mathrm{m}\Omega \cdot \text{cm}^{2}$ regrowth-free vertical $\text{GaN}$ trench MISFET featuring a high inversion channel mobility of 205 $\text{cm}^{2}/\mathrm{V}\cdot\mathrm{s}$. The vertical GaN trench MISFET can realize a normally-off operation with desirable threshold-voltage $(V_{\text{TH}})$ of 4.1 V and high ON/OFF current ratio ($I_{\text{ON}}/I_{\text{OFF}}$ at -1200 V) of ~10⁸. Thanks to the high-quality monocrystal-like AlN interfacial-layer (NIL) at the dielectric/GaN interface, interface trap density can be effectively suppressed by approximately one order of magnitude, enabling hysteresis $(\Delta V_{\text{TH}})$ reduction from $\sim 0.9\mathrm{V}$ to $\sim 0.2\ \mathrm{V}$ in 500-ns high-speed pulsed I-V characterizations. By virtue of the high-quality AlN NIL as well as the smooth trench sidewall, interface roughness and Coulomb scattering can be suppressed, leading to a high inversion channel mobility of 205 $\text{cm}^{2}/\mathrm{V}\cdot \mathrm{s}$ in the trench MISFET. The high-voltage and high-mobility vertical GaN MISFET shows great potential for high-efficiency kV-class power electronic applications.