Effects of Oxide Species on the Reduction of Contact Resistivity of Al/oxide/n-GaN MIS Devices

We investigated metal-insulator-semiconductor (MIS) contact using $\mathbf{GaO}_{\mathrm{x}},\mathbf{TiO}_{\mathrm{x}}$, and $\mathbf{ZnO}_{\mathrm{x}}$ on n- GaN having Si doping concentration of $\boldsymbol{2\times 10}^{18} \mathbf{cm}^{-3}$. While we obtained the low specific contact resistivity $(\boldsymbol{\rho}_{c})$ of $\boldsymbol{7.1\times 10^{-7}\Omega}\cdot \mathbf{cm}^{2}$ with $\mathbf{GaO}_{\mathrm{x}}$ and $\boldsymbol{7.7\times 10}^{-5}$ Ω·cm² with $\mathbf{TiO}_{\mathrm{x},}\rho_c$ increased with $\mathbf{ZnO}_{\mathrm{x}}$. We further evaluated the band alignment of oxide/GaN and discussed the variation of the Schottky barrier height (SBH) based on the metal-induced gap states (MIGS) model to validate our results.