Effect of Deposition Method on Valence Band Offsets of SiO2 and Al2O3 on (Al0.14Ga0.86)2O3

There are often variations in reported valence band offsets for dielectrics on semiconductors and some of the reasons documented include metal or carbon contamination, interfacial disorder, variations in dielectric composition, thermal conditions, strain, and surface termination effects. In this paper we show that there are differences of up to 1 eV in band alignments for the common gate dielectrics SiO2 and Al2O3 on single crystal (Al(0.14)Ga(0.8)6)(2)O-3, depending on whether they are deposited by sputtering or Atomic Layer Deposition. In the case of Al2O3, this changed the band alignment from nested (type I) to staggered gap (type II). The valence band offset at each heterointerface was measured using X-Ray Photoelectron Spectroscopy and was determined to be -0.85 +/- 0.15 eV for sputtered Al2O3 and 0.23 +/- 0.04 eV for ALD Al2O3 on beta-(Al0.14Ga0.86)(2)O-3, while for SiO2 it was 0.6 +/- 0.10 eV for sputtered and 1.6 +/- 0.25 eV for ALD. These results are consistent with recent results showing that the surface of Ga2O3 and related alloys are susceptible to severe changes during exposure to energetic ion environments. (C) The Author(s) 2018. Published by ECS.