Development of dry processing techniques for CdZnTe surface passivation

Cadmium zinc telluride (CZT) has shown great promise as a material to be used for the production of large-volume x- and gamma-ray spectrometers operating at room temperature. However, the performance of spectrometers fabricated from CZT crystals are often limited by leakage current in the devices. A method for passivating the surface of Cd1-xZnxTe (CZT) x-ray and gamma ray detectors using relatively simple dry processing techniques has been developed. Leakage currents were significantly reduced for several processing methods. CZT samples were exposed to an oxygen plasma and/or coated with a reactively sputtered silicon nitride layer. Several parameters of the oxygen plasma step were found to be important for achieving enhanced surface resistivity. SiNx has been previously characterized and was used because of its high dielectric quality and low deposition temperature. Reduction in leakage current after passivation by a factor of as much as twenty is demonstrated. Results are also presented which give a measure of the long-term stability of the passivating layers