Electrode Studies Of CdZnTe Nuclear Radiation Detector

Cadmium Zinc Telluride (Cd1-xZnxTe or CZT) single crystal is a room temperature nuclear radiation detector material with excellent properties. It can be used to fabricate X-ray andγ-ray detectors because of its high atomic number, high resistivity, low dark current,good thermal stability, wide energy band gap, and high energy resolution of the detecting ray etc. In recent years, it has given rise to much attention and become hot pot of research in the world. However, in the process of the preparation of CdZnTe room temperature nuclear radiation detector, the surface passivation of the wafers and the tehnic of electrode are the most important processes.In this paper, the two key processes were studied.It was found that, there were a lot of faulty factors on the wafers'surface when only polished mechanically and chemically, but through the passivation treatment there can be formed the oxidizing layer on the surface which has the insulation property, and it can reduce the surface leakage currents. So it is a good method to fabricate MIS structure electrode. The corroding time have decisive function to the electricity property of the wafers, according to the structure, component and performance of surface of the wafers, and we got the process which will improve the performance of CdZnTe detector, Firstly, the CdZnTe wafers were polished mechanically and chemically by means of metallographic abrasive papers and chemical etchant, then the wafers were passivated NH4F/H2O2 solution for 30 min. there formed a high resistivity layer of oxide on the surface which will lower the leakage current, and the passivated CdZnTe wafers were suitable for detector preparation. Also, we were prepare MS and MIS structure electrode with C, Pt and Au, then compared the I-V properties, and it was found that Pt and the wafer formed Schottky contact which can reduce the leakage current and increase energy resolution. Pt is the better electrode material for CdZnTe detector.The leakage current in MSM structure electrode is much higher which limited the application of the detectors of MSM structure electrode. However, the leakage current of MIS structure electrode detector is much lower than that of MSM structure.For the MIS structure electrode detector, the change of the electrode polarity for unsymmetrical electrode contact would influence the leaking current of the CdZnTe detector.