Enhancement of drain current density by inserting 3nm Al layer in the gate of AlGaN∕GaN high-electron-mobility transistors on 4in. silicon

Al Ga N ∕ Ga N high-electron-mobility transistors (HEMTs) on 4in. Si were fabricated by inserting 3nm of Al metal as a gate prior to the deposition of Pd∕Ti∕Au. The increase of drain current (IDSmax) density and decrease of extrinsic transconductance (gmmax) have been observed in the Al-gated AlGaN∕GaN HEMTs. The increase of IDmax is due to the increase of two-dimensional electron gas sheet carrier density, which was confirmed by capacitance-voltage (C-V) measurements. Moreover, the Al layer inserted-gate HEMT exhibited negative threshold voltage (Vth) shift. The Al and AlGaN interface shows Al-based oxide layer which was confirmed by Auger electron spectrum and x-ray photoelectron spectrum.