Energy barriers at interfaces between (100) In_xGa_1-xAs (0≤x≤0.53) and atomic-layer deposited Al₂O₃ and HfO₂

The electron energy band alignment at interfaces of In_xGa_1-xAs (0≤x≤0.53) with atomic-layer deposited insulators Al₂O₃ and HfO₂ is characterized using internal photoemission and photoconductivity experiments. The energy of the In_xGa_1-xAs valence band top is found to be only marginally influenced by the semiconductor composition. This result suggests that the known 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. It finds support from both electron and hole photoemission data. Similarly to the GaAs case, electron states originating from the interfacial oxidation of In_xGa_1-xAs lead to reduction in the electron barrier at the semiconductor/oxide interface.