Band-Bending of Ga-Polar GaN Interfaced with Al₂O₃ 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/O₃) treatment of the GaN surface on the energy band bending of atomic-layer-deposition (ALD) Al₂O₃ coated Ga-polar GaN were studied. The UV/O₃ 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 Al₂O₃/GaN interfaces. The UV/O₃ treatment increases the surface energy of the Ga-polar GaN, improves the uniformity of Al₂O₃ deposition, and changes the amount of trapped charges in the ALD layer. The positively charged surface states formed by the UV/O₃ treatment-induced surface factors externally screen the effect of polarization charges in the GaN, in effect, determining the eventual energy band bending at the Al₂O₃/GaN interfaces. An optimal UV/O₃ treatment condition also exists for realizing the "best" interface conditions. The study of UV/O₃ treatment effect on the band alignments at the dielectric/III-nitride interfaces will be valuable for applications of transistors, light-emitting diodes, and photovoltaics.