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Abstract CdZnTe crystal has proved to be an excellent material to detect X-ray and gamma ray. Ohmic electrode on CdZnTe wafer is one of the key factors during the fabrication of CdZnTe detector. In this work, the effect of Au/Cd composite electrode on the (111)B (Te-rich surface) of CdZnTe wafers with p-type conductivity (p-CdZnTe) was investigated. The Au/Cd electrode was deposited on the (111)B of CdZnTe wafers by vacuum evaporation method. For comparison, the Au/Zn and Au electrodes were also deposited on CdZnTe (111)B surfaces. The surface and structural properties of the composite electrodes on the (111)B surface of CdZnTe were characterized by the AFM, XPS and SEM. The electrical properties of the electrodes were evaluated by Current-Voltage (I-V) test. The results show that the surfaces of the Au/Cd and Au/Zn electrodes on (111)B surface were more smooth with less foreign impurities among the interface of the electrode and CdZnTe, as compared to the Au electrode on (111)B surface. The Au/Cd composite electrode can obtain a more ideal ohmic contact than Au/Zn composite electrode on the (111)B surface of CdZnTe wafer. The Au/Cd composite electrode on (111)B surface has the lowest Schottky barrier height, which is attributed to the reduction of the influence of Te enriched surface on the metal-semiconductor contact. [ABSTRACT FROM AUTHOR]

The effect of different point defects in CdZnTe (CZT) crystals on carrier transport performance were discussed. The energy level and concentration of the traps were determined by the photo-induced current transient spectroscopy (PICTS). By adding the infrared light illumination into the PICTS experiment, the effect of sub-bandgap light on defects was observed. Meanwhile, several DC photoconductive experiments were done under different wavelength lights were used to explore the effect of the different defects on carrier transport properties of CZT crystals. Furthermore, the energy spectrum test was used to investigate the effect of sub-bandgap light on the energy resolution of CZT detectors. The data results showed that sub-bandgap light could effectively change the ionization state of defects. The doubly ionized Te antisite (Te Cd 2+) had the greatest effect on mobility-lifetime product(μτ) of electrons owing to its stronger ability of capturing electrons and energy level located around the midgap. While the secondary ionized Cd vacancy (V Cd 2−), as considered as a hole trap, had the greatest effect on μτ-product of holes. Consequently, choosing suitable infrared light can improve the detection performance of CZT crystal effectively. [ABSTRACT FROM AUTHOR]

The effect of inductively coupled Ar plasma etching (ICP-Ar) instead of traditional Br–MeOH etching on the performance of CdZnTe detectors was studied. The optimal ICP etching parameters were determined by experiments. The XPS results indicated that the surface composition of CdZnTe etched by ICP-Ar had no obvious TeO x peak and was closer to stoichiometric ratio than that etched by Br–MeOH. The leakage current of ICP-Ar etched CdZnTe surface was significantly reduced, and the detection performance with the energy resolution was improved by 12%, as compared to Br–MeOH etched sample. Moreover, ICP-Ar etching abandoned the drawbacks of Br–MeOH by producing corrosive gases, making it safer and more environmentally friendly. Therefore, inductively coupled Ar plasma etching is expected to replace Br–MeOH etching and become an effective method for CdZnTe surface treatment. [ABSTRACT FROM AUTHOR]