Excitation spectra of defect levels derived from photoinduced current transient spectroscopy — a tool for studying deep levels in Cu(In,Ga)Se2 compounds

Energy required for the optical excitation of carriers onto defect levels is a parameter that compliments thermal activation energy and helps to understand the electronic properties of defects under study. Here a modification of the photoinduced current transient spectroscopy (PICTS) based on phase-sensitive detection is proposed which makes possible to measure the excitation spectra of defect levels. The representative results of the excitation spectra of the epitaxial CuGaSe2 and polycrystalline Cu(In,Ga)Se2 thin films are presented. They illustrate the usefulness of the method as a tool for studying defect properties by providing data that supplement information derived from standard PICTS spectroscopy.