¢ò - ¢ö Compounds Crystal Defects And Annealing Modified

There are several kinds of defects including point defects, dislocations, Te precipitates and Zn segregation in the as-grown CdZnTe crystals. These defects are veiy harmful to the application of CdZnTe as the substrate of HgCdTe film epitaxy. It is expected to eliminate the defects through annealing. Observation on the variation of surface morphology during the etching process indicates that the grain boundary and Te pecipitates will be shown earlier than the dislocatins. The measurements on the microstructure, IR transmission, rocking curve and the composition distribution reveal that the defects and the properties of CdZnTe crystals change in a quite large region for the slices from different ingot, or even for different wafers of the same ingot. More than one kind of defects are often gathered together. To improve the properties of the crystals, slices are first annealed using a two step method. The most obvious change in the properties of CdZnTe wafers after annealing are the increase of IR transmission, the broadening in FWHM(full width at half-maximum) of rocking curves. The morphologes of Te precipates are changed after annealing. A new kind of defect similar to the twins on surface is also observed. Several annealing experiences are done by changing the annealing time, annealing temperature and the cooling rate. The effects of different annealing sequences on the CdZnTe properties are analysed. A special low temperature annnealing method at 4000C shows a great efficiency for improving the IR transmission properties and keeping the crystallity.