Performance study of CdZnTe spectrometers

The basic understanding as well as the technology of wide band-gap semiconductors in II–VI group in general; and in CdZnTe in particular, are still at an early stage of investigation and are not established. In this research new models were developed to describe the charge collection in semiconductor spectrometers for X- and γ-rays as well as for particles. For the first time a model was developed to describe analytically or numerically the variance in the charge collection efficiency as a function of energy. A methodology has been developed, allowing to evaluate electrical properties of the semiconductor based on spectroscopy measurements. The issue of passivation for wide band-gap CdZnTe spectrometers has been found to be of great importance and we report it for the first time. We have shown that the leakage current in resistive CdZnTe spectrometers is mainly a surface effect. For the first time the noise power spectral density of the spectrometers was characterized and correlated to the spectrometer technology including contacts, crystal growth technique and passivation.