Suppression of Gate Leakage and Enhancement of Breakdown Voltage Using Thermally Oxidized Al Layer as Gate Dielectric for AlGaN/GaN Metal--Oxide--Semiconductor High-Electron-Mobility Transistors

A synthetic route for alumina based dielectric layer for AlGaN/GaN metal--oxide--semiconductor high-electron-mobility transistors (MOS-HEMT) has been developed. The approach is based on oxidative annealing of thin Al layer deposited prior to Schottky gate metallization. The MOS-HEMT exhibits good pinch off features with $I_{\text{ds-max}}$ and $g_{\text{m-max}}$ of 421 mA/mm and 121 mS/mm, respectively. Frequency dependent conductance measurements yielded a minimum trap density ($D_{\text{T}}$) and trap transient time ($T_{\text{T}}$) of $2.2 \times 10^{12}$ cm -2 eV -1 and 1.3 μs, respectively. The oxide layer suppresses the gate leakage by two orders of magnitude and enhances the breakdown voltage ($\mathit{BV}$) of the devices. A high $\mathit{BV}$ of 431 V and figure of merit (FOM) of $1.89 \times 10^{8}$ V 2 $\Omega^{-1}$ cm -2 for 15 μm device at ($L_{\text{gd}} \leq 4$ μm) was observed for Al 2 O 3 based MOS-HEMT.