Effect of Oxygen-Related Defects on Electrical Properties of Cd_0.9Zn_0.1Te Semiconductor

The impurity from raw material in the as-grown crystal is one of the most important factors that hamper the advancement of Cd_0.9Zn_0.1Te (CZT) detectors. However, the influence of impurity oxygen is rarely reported. In this study, the first principle calculation is carried out to give a prediction about transition levels of oxygen-related defects. Glow discharge mass spectrometry (GDMS) is used to determine the concentration of all the elements. The quantitative analysis of oxygen-related defects is carried out by deep-level transient spectrum (I-DLTS), which can break through the limitations of traditional C-DLTS testing in the field of high-resistance materials. The peaks observed at about 50 and 100 K are related to the level of (VCd-O_Te)^0/- and (VCd-O_Te)^-/2- defect pair, with energy about E_v +0.079 eV and E_V +0.173 eV, trap cross section about 3.02× 10^-19 and 1.01× 10^-19 cm2, respectively. The effect of oxygen on (μ τ)_e of the CZT semiconductors is evaluated through Alpha particle spectrum response testing by fitting the charge collection efficiency with applied bias voltages. The (μ τ)_e is about 5.21× 10^-4 cm2/V in CZT with more oxygen and 2.33× 10^-3 cm²/V with less oxygen. The mobility is obtained from the results of the time of flight (TOF) testing through the laser-beam-induced current (LBIC) technique, to be around 1000 cm²/Vċ s1 for both samples, and the lifetime to be 494 and 2407 ns, respectively. It can be concluded that oxygen-related defects can terribly affect the electron transport properties.