In this study, the authors systematically investigate the electrical properties and reliability of Al2O3/SiO2 nanolaminate films with different compositions on GaN. Leakage current in the nanolaminates was suppressed by the higher SiO2 content due to the enhancement of conduction band offset between the nanolaminate and GaN. The interface-trap density (Dit) at the nanolaminates/GaN was as good as those at the Al2O3/GaN and SiO2/GaN interfaces. The lifetime of the nanolaminates increased with increasing SiO2 content. In addition, the authors demonstrated that the nanolaminate with thickness ratio of 0.21 had almost same lifetime as the Al2O3 under same equivalent electric field.

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We carried out nondestructive measurements of the depth profile of etching-induced damage in p-type gallium nitride (p-GaN), in particular surface band bending, using Hard X-ray Photoelectron Spectroscopy (HAX-PES). HAX-PES at different take-off angles of photoelectrons made it clear that etching by inductively coupled plasma (ICP) introduced donor-like states in a surface layer of GaN. We were able to quantitatively analyze band bending and charge distribution in an etched p-GaN. The analysis results indicated the existence of deep donors with a concentration of 1-2 Â 10 20 cm À3 in a surface layer whose thickness increased with increasing a bias power of ICP.

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