Dopant-induced band filling and bandgap renormalization in CdO: In films

The effect of carrier concentration on the Fermi level and bandgap renormalization in over 30 indium-doped cadmium oxide (CdO:In) films with carrier concentrations ranging from 1 to 15×1020 cm-3 was studied by using the two band k·p model with electron-electron and electron-ion interactions. It is shown that the Tauc relation, which is based on parabolic valence and conduction bands, overestimates the optical bandgap in CdO films. Theoretical calculations of the optical bandgap give good agreement with experiments by taking into account the Burstein-Moss effect for a nonparabolic conduction band and bandgap renormalization effects. The band filling and bandgap renormalization in these CdO:In films are about 0.5~1.2 eV and 0.1~0.3 eV, respectively.