Suppression of gate leakage current in GaN MOS devices by passivation with photo‐grown Ga 2 O 3

We report the use of photo‐enhanced chemical (PEC) technique to form high‐quality metal oxide semiconductor (MOS) devices made of gallium oxide (Ga 2 O 3 )/gallium nitride (GaN). Gate leakage current density as low as 2×10 –7 A/cm 2 at a bias field up to 2 MV/cm is observed in the GaN MOS devices that are formed by novel PEC wet etching and have the top surface and mesa sidewall passivated by the photo‐grown Ga 2 O 3 . The depth‐resolved X‐ray photo‐emission spectra (XPS) and atomic‐ratio analysis indicate that a intermediate and thin ∼20 nm GaON layer of graded composition forms the Ga 2 O 3 /GaON/GaN system, which releases the interfacial strain and thus minimizes the density of interfacial states. The IV and high‐frequency CV analyses reveal that the Ga 2 O 3 layer can sustain an electrical breakdown field of 3.5 MV/cm and the structures have a low density of interfacial state (D it ) in the order of 10 11 eV –1 cm –2 . We attribute these results to the immunity to surface damage by the novel PEC wet etching and the effective passivation on mesa sidewall and surface formed by the photo‐grown Ga 2 O 3 . (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)