DETERMINATION OF STRUCTURE DEFECTS IN MERCURY CADMIUM TELLURIDE MULTILAYER MATERIALS. Fuju Yu, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China.

Some structure defects at heterojunction regions, such as microtwins, stacking faults, mismatch dislocations, and orientation differences between multilayer structures: mercury cadmium telluride/cadmium telluride and cadmium telluride/gallium arsenide as well, were studied by TEM (transmission electron microscopy). For the heterojunctions of mercury cadmium telluride/ cadmium telluride/gallium arsenide multilayers gown by MBE (molecular beam epitaxy) method, it is clearly shown that the buffer layer cadmium telluride acts as an effective barrier for mercury cadmium telluride epilayer for most of structure defects, and orientation differences between multilayer structures mercury cadmium telluride/cadmium telluride and cadmium telluride/gallium arsenide were found to be the more orientation difference accompanies the more lattice mismatch degree. There is a transient layer with intensive strain and a thickness at about 30 Angstrom, between buffer layer cadmium telluride and substrate. The transient layer distributed near homogeneously over a large area was just happened at the beginning of epitaxial growth of buffer layer due to large lattice mismatch as well as inappropriate growth rate ( perhaps too fast) or other insufficient condition. It seems likely that the transient layer relaxes the lattice mismatch strain at heterojunction cadmium telluride/gallium arsenide, therefore no mismatch dislocation was created during the following growth of buffer layer and the epilayer could be smoothly grown afterwards. It is surprising to find that the epilayer can still be formed in an epitaxial orientation upon this transient layer, and this suggests either that the substrate can influence the overgrowing epilayer through the intervening layer, or that this layer forms interactively later, just similar to the case in the (cadmium, zinc)sulfide/gallium arsenide compounds.