Energy-band parameters of atomic layer deposited Al2O3 and HfO2 on InxGa1−xAs

X-ray photoelectron spectroscopy (XPS) combined with reflection electron energy loss spectroscopy (REELS) were used to determine the energy-band parameters, valence-band offsets ΔEV, conduction-band offsets ΔEC, and energy-band gaps Eg, of the atomic layer deposited (ALD) Al2O3 and HfO2 on InxGa1−xAs (x=0, 0.15, 0.25, and 0.53). Using REELS, Eg values of the ALD-Al2O3 and –HfO2 were estimated to be 6.77 and 5.56±0.05 eV, respectively. The ΔEV’s were determined by measuring the core level to valence band maximum binding energy difference from the XPS spectra. The ΔEC’s were then extracted from ΔEV’s and the energy-band gaps of the oxides and InxGa1−xAs, and are in good agreement with those estimated from the Fowler–Nordheim tunneling. The ΔEC’s and ΔEV’s are larger than 1.5 and 2.5 eV, respectively, for all the ALD-oxide/InxGa1−xAs samples.