Evaluation of zinc telluride as a gamma detector for high temperature applications

An evaluation of zinc telluride was made from the point of view of device fabrication for using it as a gamma detector at high temperatures. Polycrystalline as well as single crystal material was used. Following material characterization, ohmic contacts were made using both gold and silver. Silver contacts were found to suffer severe degradation after high temperature cycling. Gold contacts also showed some degradation after heating. New copper-gold contacts were made and found to remain stable even after high temperature cycling. These contacts exhibited a reasonably low contact resistivity of about 0.3 ohm-cm2. An attempt was made to fabricate MIS structures using aluminum and indium. After suitable heat treatment aluminum showed good forward characteristics but the reverse breakdown voltage was low and leakage current was quite high. Indium devices generally showed poor diode behavior. The current conduction mechanism was determined to be space charge limited. Gamma attenuation in zinc telluride was experimentally found to be better than that of silicon. Devices made from zinc telluride did not show any detection for gamma rays or alpha particles. This is attributed to a large number of defects, small carrier lifetime, a wide transition region and high leakage current which prevented the application of large electric fields