Low interface state density AlGaN/GaN MOSHFETs with photochemical vapor deposition SiO2 layers

High quality SiO2 was successfully deposited onto AlGaN by photo chemical vapor deposition (photo-CVD) using D2 lamp as the excitation source. It was found that the interface state density was only 1.1 × 1011 cm−2 eV−1. AlGaN/GaN metal–oxide–semiconductor heterojunction field effect transistors (MOSHFETs) were also fabricated with such photo-CVD oxide as the insulating layer. Compared with AlGaN/GaN metal–semiconductor HFETs (MESHFETs) with similar structure, it was found that we could reduce the gate leakage current by more than four orders of magnitude by inserting the 32 nm-thick photo-CVD SiO2 layer between AlGaN/GaN and gate metal. With a 1 μm gate length, it was found that room temperature saturated Ids, maximum gm and gate voltage swing (GVS) of the fabricated nitride-based MOSHFET are 800 mA/mm, 86 mS/mm and 9 V, respectively. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)