Postgrowth thermal treatment of CuIn(Ga)Se2: Characterization of doping levels in In-rich thin films

Abstract

Optical and electrical measurements were carried out on annealed CuIn(Ga)Se2 (CIGS) thin films with Ga content of 10%. Annealing of as-grown In-rich CIGS in air/oxygen at 400 °C changes the photoluminescence spectrum to a spectrum which is usually obtained from as-grown Cu-rich CIGS. The annealing step reduces the donor density and the high compensation. This effect allows the investigation of the defect levels of In-rich CIGS which is not possible in as-grown layers due to the dominating fluctuating potentials. The activation energies for the donors and acceptors in In-rich CIGS were found to be 10 and 75 meV, respectively. The densities are in the order of 1018 cm−3 each, with a compensation ratio of 0.99.