FORMATION AND CONTROL OF DEFECTS DURING MOLECULAR-BEAM EPITAXIAL-GROWTH OF HGCDTE

Void defects were demonstrated to form away from the substrate-epifilm interface during the molecular beam epitaxial growth of mercury cadmi um telluride on cadmium zinc telluride substrates. These were smaller in size compared to voids which nucleated at the substrate-epifilm int erface, which were also observed. Observations of void nucleation away from the substrate-epifilm interface were related to the respective g rowth regimes active at the time of the void nucleation. Once nucleate d, voids replicated all the way to the surface even if the flux ratios were modified to prevent additional nucleation of voids. For a signif icant number of films, void defects were observed co-located with hill ocks. These voids were usually smaller than 1 mu m and appeared almost indistinguishable from unaccompanied simple voids. However, these voi d-hillock complexes displayed a nest of dislocation etch pits around t hese defects upon dislocation etching, whereas unaccompanied voids did not. The nests could extend as much as 25 mu m from the individual vo id-hillock complex. The density of dislocations within the nest exceed ed 5 x 10(6) cm(-2), whereas the dislocation density outside of the ne st could decrease to <2 x 10(5) cm(-2). The void-hillock complexes for med due to fluctuations in growth parameters. Elimination of these flu ctuations drastically decreased the concentrations of these defects.