Dislocations in HgCdTe (111)B films

The dislocations in HgCdTe films grown by LPE on CdZnTe (111)B substrates were studied by chemical etching. Among the etchants used for HgCdTe materials before, it was found that the Schaake etchant was an effective method to reveal the dislocations of HgCdTe (111)B films with a thickness over 5μm. Besides of the threading dislocations as reported before, another kind of dislocations induced by the stress was also observed by using Schaake etchant. Large quantities of such dislocations were observed in the areas nearby the melt droplet left on the LPE film and cutting line and on the surfaces of the HgCdTe films annealed by using a cap layer and unsuitable transportation of samples. The measurements of the depth profiles of the EPDs show that the most of the stress-induced dislocations are located in the surface layer and its density can be as high as 107cm-3. Whereas the EPD of the threading dislocation doesn't change a lot along the depth of the film in usual case. The Chen etchant can also be used to reveal the threading dislocations of the films thicker than about 10μm. The phenomena of two kinds of etch pits was also observed on the surface of HgCdTe film etched by the Chen etchant. The etch pit densities originated from threading dislocations are approximately the same for both etchants. But the stress-induced dislocations in the surface layer were not observed by using the Chen etchant except the area near the melt droplet.