Modulated photocurrent experiments-comparison of different data treatments

Abstract

Modulated Photocurrent experiments provide a powerful tool to characterize localized defect states within the band gap of semiconductors. However, in recent years, different data analysis methods have been established. The method proposed by Herberholz et al. identify defect positions and attempt-to-escape frequencies considering the phase shift between excitation flux and measured photo current only. In contrast, Brüggemann et al. propose to use phase shift and amplitude of the modulated photo current to resolve an energy dependent density of trap states. This work compares both analysing procedures. We demonstrate that for simple and dominant defects, such as acceptor or donor like monovalent traps, both methods give equivalent results. However, the Herberholz method fails for more complex defect arrangements as exemplified on hydrogenated amorphous silicon or polycrystalline CuInSe2.