The role of material uniformity and device geometry on cadmium zinc telluride room-temperature nuclear spectrometer performance .

摘要

Cadmium Zinc Telluride (Cd1-xZnxTe or CZT) is a relatively new semiconductor material which shows great promise as a room-temperature radiation detector. It was developed to operate in a regime between two mature technologies (scintillators and cryogenically cooled semiconductor devices). It is hoped that once mature, CZT radiation spectrometers will give better energy resolution than the current room temperature radiation detector technology (scintillators) and operate without cryogenic cooling, unlike high purity Ge (HPGe). The current state of CZT growth techniques poses two barriers to the production of inexpensive, large volume spectrometers. The material is often polycrystalline, and a large variation in the charge carrier transport properties is observed throughout an ingot. Additionally, even the best quality material usually exhibits hole transport properties which are barely adequate for a spectrometer. Overall, the material commercially available is often multi-grain with large variation in the electron and hole transport properties, which is suboptimal for most detector applications.;I have examined the effects of material non-uniformity on the performance of CZT radiation detectors. In particular, I have identified the effect a crystalline boundary will have on the performance of a CZT device. I have also performed a theoretical analysis on the expected performance as a function of charge transport properties. The theoretical discussion of the charge transport effects covers the range observed in currently available material and shows how improvements in hole transport will affect performance. Finally, I have examined several novel devices designed to compensate for the poor hole transport properties in CZT. These results along with several material characterization techniques are presented in this dissertation.