On the band-structure lineup at Ga2O3, Gd2O3, and Ga2O3(Gd2O3) heterostructures and Ga2O3 Schottky contacts

The interface-induced gap states (IFIGS) are the fundamental mechanism that determines the band-structure lineup at semiconductor interfaces, i.e., the band-edge offsets at semiconductor heterostructures and the barrier heights of metal–semiconductor or Schottky contacts. Both quantities are composed of a zero-charge transfer and an electrostatic-dipole term which are given by the IFIGS’s branch-point energies and the electronegativities of the two solids in contact, respectively. A respective analysis of experimental valence-band offsets of Ga2O3 and Gd2O3 heterostructures results in the empirical p-type branch-point energies of 3.57 and 2.85 eV, respectively. From experimental barrier heights of n-Ga2O3 Schottky contacts an empirical n-type branch-point energy of 1.34 eV is obtained. The p- and n-type branch point energies of Ga2O3 add up to 4.91 eV, the width of the Ga2O3 band gap, as to be expected from the theoretical IFIGS-and-electronegativity concept. The experimental valence-band offsets of Ga2O3(Gd2O3) heterostructures indicate that at their interfaces the chemical composition of the oxide differs from its nominal value in the bulk.