Investigation of Electncal Contacts for Gd,-,Zn,Te Nuclear Radiation Detectors)

A comparative study of four merent metal deposition methods on detector grade Cd,,Z%Te crystal has been done using current-voltage (I-V) characterization and 133Ba gamma spedroscopy. Electroless Au contact and thermal evaporated Au contact have been found to yield a smaller leakage current and a more headsymmetric I-V curve than that of sputtered Pt and Au contact. An optimum detector performance can be acheved by combining the thermal evaporated Au deposition method with a chemical surface treatment consisting of S%Br-MeOH followed by 2% Br-20% lactic acid in ethylene glycol. Low temperature photoluminescence spectra of Cd,-.J%Te samples correspondmg to these Werent metallization schemes are also presented and discussed. During the past few years, Cadmium ZincTellwide (Cd,..JqTe) has rapidly captured a significant interest due to its high potential for many room temperature nuclear radiation detector applications. Like many other semiconductors, the quality of a final Cd,,Z%Te detector depends heavily on every single step in the fabrication process. Of great importance is the surface treatment and contacting which affects the applied electric field and to a large extent, the defkct states, both extrinsic and intrinsic of the nearsurface region. These factors determine the surface leakage current whch in turn sigmkicantly affects the performance of the device. Yet. due to a very limited number of reports we felt that a comparative study on the selection of electrode materials, contact deposition methods and surface treatments of Cd,,Z%Te detector performance is needed. In this paper, we present a study of the correlation between dark leakage current and electrical contacts and the contacting procedure, together with an analysis on the impact on the detector performances.