A new technique to decompose closely spaced interface and bulk trap states using temperature dependent pulse-width deep level transient spectroscopy method: An application to PT/CdS photodetector

Abstract

A novel method is presented here to experimentally decompose nonexponential capacitive transients into the appropriate components from the closely spaced deep trap states. Using temperature dependent pulse-width deep level transient spectroscopy (TDP-DLTS) technique, we show for the first time that two bulk trap states and one continuously distributed interface states in (Pt/CdS) photodiodes can be successfully separated. The basic principle is to set the applied pulse width to follow an averaged temperature-dependent capture time constant and divide the DLTS spectrum. In the example of Pt/CdS photodiodes, we show that all physical parameters including thermal activation energies, capture cross sections, and trap densities are more accurately calculated after each component is separated from others. The origins for those bulk traps and interface states are also discussed. Without any complicated mathematics or program, TDP-DLTS can be applied to both large and small voltage pulse DLTS measurements.