Band-Bending of Ga-Polar GaN Interfaced with AlO through Ultraviolet/Ozone Treatment.

Understanding the band bending at the interface of GaN/dielectric under different surface treatment conditions is critically important for device design, device performance, and device reliability. The effects of ultraviolet/ozone (UV/O) treatment of the GaN surface on the energy band bending of atomic-layer-deposition (ALD) AlO coated Ga-polar GaN were studied. The UV/O treatment and post-ALD anneal can be used to effectively vary the band bending, the valence band offset, conduction band offset, and the interface dipole at the AlO/GaN interfaces. The UV/O treatment increases the surface energy of the Ga-polar GaN, improves the uniformity of AlO deposition, and changes the amount of trapped charges in the ALD layer. The positively charged surface states formed by the UV/O treatment-induced surface factors externally screen the effect of polarization charges in the GaN, in effect, determining the eventual energy band bending at the AlO/GaN interfaces. An optimal UV/O treatment condition also exists for realizing the "best" interface conditions. The study of UV/O treatment effect on the band alignments at the dielectric/III-nitride interfaces will be valuable for applications of transistors, light-emitting diodes, and photovoltaics.