21 November 2000 Contactless measurements of charge traps and carrier lifetimes in detector-grade cadmium zinc telluride and mercuric iodide
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An understanding of compensation and trapping in Cd1-xZnxTe and HgI2 is necessary in order to improve the size and spectroscopic performance of radiation detectors fabricated from these materials. Although several electron and hole traps have been identified, very little is currently understood about the effect of specific carrier traps on the mean free path of the charge carriers. Characterization techniques such as Thermally Stimulated Current (TSC) or Thermoelectric Emission Spectroscopy (TEES) have been used for trap identification, while time-of-flight techniques have been employed to determine carrier mobility and lifetime but it has proven difficult to correlate the results of these independent measurements. Furthermore, these characterization methods are complicated by the need to make electrical contacts to the material. Here we report on contactless, thermally stimulated lifetime measurements performed on detector-grade Cd1- xZnxTe (x approximately 0.1) and HgI2 crystals using a microwave cavity perturbation method. The microwave technique is complimentary to contact-based methods and provides both trap identification and lifetime determination in a single measurement. The results provide evidence of lifetime-limiting deep traps in these materials. The trap activation energies and the minimum detrapping times are estimated and the results are compared to previous TSC and TEES investigations.
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Gary C. Tepper, Gary C. Tepper, Royal Kessick, Royal Kessick, Ralph B. James, Ralph B. James, Lodewijk Van den Berg, Lodewijk Van den Berg, } "Contactless measurements of charge traps and carrier lifetimes in detector-grade cadmium zinc telluride and mercuric iodide", Proc. SPIE 4141, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics II, (21 November 2000); doi: 10.1117/12.407568; https://doi.org/10.1117/12.407568


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