Influence of substrate orientation on the growth of HgCdTe by molecular beam epitaxy

An empirical study is reported, wherein HgCdTe was deposited simultaneously on multiple CdZnTe substrates of different orientations by molecular beam epitaxy. These orientations included the following vicinal surfaces: (115)B, (113)B, (112)B, and (552)B. Additionally, growth on (111)B was explored. Growth conditions found to be nearly optimal for the standard (112)B orientation were selected. Through a series of growth runs, substrate temperature was varied, and the physical properties of the resulting HgCdTe epilayers were measured. These measurements included Nomarski microscopy, infrared transmission, x-ray diffraction, and defect decoration etching. The properties of HgCdTe epilayers as a function of temperature were roughly similar for all vicinal surfaces. Namely, as the temperature increased, the dislocation density decreased. At some critical temperature, the density of void defects increased dramatically. This critical temperature varied with orientation, the (115)B exhibiting the lowest critical temperature and the (112)B and (552)B exhibiting the highest. The (115)B, (113)B, and (112)B orientations exhibited "needlelike" defects on the as-grown HgCdTe surface. The density of these defects decreased with increasing temperature. The (552)B surface exhibited no such defects and growth behavior nearly identical to the (112)B growth surface. [PUBLICATION ABSTRACT]