<title>Structural defects and impurities on CZT crystals</title>

Abstract

Various types of precipitates and grain boundaries have been studied in Cd1-xZnxTe (CZT). In this study we used elemental analysis methods such as scanning electron microscopy (SEM), microprobe analysis, inductively coupled plasma mass spectroscopy (ICP/MS) and the new laser ablation ICP/MS methods. Transient charge technique was applied for the first time of CZT crystals for evaluating the electrical transport properties of semiconductors. Another method, IR transmission spectroscopy, enables us to evaluate the microstructure defects and then to correlate this with impurity level and electrical properties in order to have a better understanding of the requirements to improve the yield for large volume CZT spectrometers. We have evaluated crystals from the former Soviet Union, which have high concentration of defects. Precipitates and grain boundaries rich with carbon were observed in CZT crystals. Electrical transport properties such as (mu) (tau) (mobility-lifetime product) were measured and correlated with the chemical physical defects, as observed by IR transmission. On crystals rich with many microstructures, as shown by IR transmission, lifetimes below 1 microsecond(s) were measured, compared with 5 - 15 microsecond(s) on the detector grade materials. SEM and microprobe analysis performed on the precipitates gave high values of carbon. However, using laser ablation ICP/MS, a value in the range of 200 - 800 ppm for carbon was measured.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.