Gate insulation and drain current saturation mechanism in InAlN∕GaN metal-oxide-semiconductor high-electron-mobility transistors

Abstract

The authors investigate $2\mu \mathrm{m}$ gate-length $\mathrm{In}\mathrm{Al}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ metal-oxide-semiconductor high-electron-mobility transistors (MOS HEMTs) with $12\mathrm{nm}$ thick ${\mathrm{Al}}_2{\mathrm{O}}_3$ gate insulation. Compared to the Schottky barrier (SB) HEMT with similar design, the MOS HEMT exhibits a gate leakage reduction by six to ten orders of magnitude. A maximal drain current density $(I_{\mathit{DS}}=0.9\mathrm{A}∕\mathrm{mm})$ and an extrinsic transconductance $(g_{me}=115\mathrm{mS}∕\mathrm{mm})$ of the MOS HEMT also show improvements despite the threshold voltage shift. An analytical modeling shows that a higher mobility of electrons in the channel of the MOS HEMT and consequently a higher number of electrons attaining the velocity saturation may explain the observed increase in $g_{me}$ after the gate insulation.