Effect of Cu deficiency on the defect levels of Cu0.86In1.09Se2.05 determined by spectroscopic ellipsometry

Abstract

Room temperature spectroscopic ellipsometry measurement of Cu0.86In1.09Se2.05 reveals that shallow defect states are found in the sub-band-gap region. The energies of these defect levels are in quantitative agreement with those calculated and measured by photoluminescence, electrical conductivity, optical absorption, and deep level transient spectroscopy at low temperatures. The results can be explained in terms of the defect physics of this material and suggest that the defect levels are due to Cu deficiency. This work opens up the possibility of measuring defect levels of off-stoichiometric or heavily doped semiconductors by spectroscopic ellipsometry at room temperature.