Band offsets at interfaces of (1 0 0)InxGa1−xAs (0 ⩽ x ⩽ 0.53) with Al2O3 and HfO2

The electron energy band alignment at interfaces of InxGa1−xAs (0 ⩽ x ⩽ 0.53) with atomic-layer deposited insulators Al2O3 and HfO2 is characterized using combined measurements of internal photoemission of electrons and photoconductivity. The measured energy of the InxGa1−xAs valence band top is found to be only marginally influenced by the semiconductor composition. This result suggests that the observed bandgap narrowing from 1.42 to 0.75 eV when the In content increases from 0 to 0.53 occurs mostly through downshift of the semiconductor conduction band bottom. Electron states originating from the interfacial oxidation of InxGa1−xAs lead to reduction of the electron barrier at the semiconductor/oxide interface.