Photo-Induced Current Transient Spectroscopy in High-Resistivity Bulk Material. I. Computer Controlled Multi-Channel PICTS System with High-Resolution

Abstract

A computer controlled multi-channel PICTS system which allows one to detect many deep trapping levels in high-resistivity bulk material by only a single thermal scanning process, has been developed. In order to obtain the normalized PICTS signal, an automatic gain controlled pre-amplifier has been used. An expanded-scale technique which allows one to distinguish fine PICTS peaks has been proposed. This expanded-scale technique is very useful especially for the case when many PICTS peaks are closely superposed. In high-resistivity bulk CdS single crystal, it has been found that PICTS spectrum-shape and number of detected peaks depend strongly upon the wavelength of exciting laser light, and that the trap-parameters obtained are not strongly influenced by light intensity. The PICTS method may be superior on many points, especially in peak-separation, to the thermally stimulated current method.