Analyzed On Defects And Stress Measurement Cd_0.96Zn_0.04Te Crystals

There exist several kinds of defects including point defects, dislocations, Te precipitates and Zn segregation in the as-grown CdZnTe crystals. These defects are very harmful to the application performance of CdZnTe as the substrate of HgCdTe epitaxy film. The forecasting and analysis of these defects are then of prime importance in order to improve the properties of the CdZnTe crystals.To improve the properties of the CdZnTe crystals, slices were first annealed using a two-step method. From the most obvious change in the properties of CdZnTe wafers after annealing, the efficiency of annealing method for improving the properties of the crystals was confirmed. But the low temperature and long-time annealing did not increase IR transmission, but decrease it. This is due to the release of Te and impurities in Te precipitates, during annealing.The Te-rich phases in the annealed CdZnTe crystals were observed by Scanning Electronic Microscope (SEM). It was found that large Te-rich phases gathered at the surface of the slices through thermo-migration during annealing, and the migration rate increased with the heating rate.The dislocations and Te precipitates in CdZnTe crystals were detected with Transmission Electron Microscope (TEM). The dislocation loops were found to be associated with Te precipitates.A new method based on X-ray diffraction was developed to measure the stress ofsingle crystal. A multiple regression model was built to calculate the Bragg angle θ0.The results indicated that the calculated stresses in the as-grown CdZnTe single crystal with heavy defects were 103MPa, and the lattice distortion was 10-3~10-1.