Photo-CVD SiO2 layers on AlGaN and AlGaN-GaN MOSHFET

High-quality SiO₂ was successfully deposited onto AlGaN by photochemical vapor deposition (photo-CVD) using a D₂ lamp as the excitation source. The resulting interface state density was only 1.1 × 10¹¹ cm^-2eV^-1, and the oxide leakage current was dominated by Poole-Frenkel emission. Compared with AlGaN-GaN metal-semiconductor HFET (MESHFETs) with similar structure, the gate leakage current is reduced by more than four orders of magnitude by using the photo-CVD oxide layer as gate oxide in AlGaN-GaN metal-oxide-semiconductor heterojunction field-effect transistors (MOSHFETs). With a 2-μm gate, the saturated I_ds, maximum g_m and gate voltage swing (GVS) of the fabricated nitride-based MOSHFET were 572 mA/mm, 68 mS/mm, and 8 V, respectively.