Isolation and control of voids and void-hillocks during molecular beam epitaxial growth of HgCdTe

Formation of small voids and defect complexes involving small voids during the molecular beam epitaxial growth of mercury cadmium telluride on cadmium zinc telluride was investigated. Some of these defects were demonstrated t o form away from the substrate-epi interface. Other defects were demonstrat ed to close before reaching the top surface without leaving any perturbatio ns on the surface, thus remaining completely hidden. The voids, which forme d away from the substrate-epifilm fixed interface, nucleated on defects int roduced into the film already grown, leading to the formation of defect com plexes, unlike the voids which nucleated at the substrate-epifilm fixed int erface. These defect complexes are decorated with high density dislocation nests. The voids which closed before reaching the film surface usually also nucleated slightly away from the film-substrate interface, continued to re plicate for a while as the growth progressed, but then relatively rapidly c losed off at a significant depth from the film surface. These voids also ap peared to form defect complexes with other kinds of defects. Correlations b etween these materials defects and performance of individual vertically int egrated photodiode (VIP) devices were demonstrated, where the relative loca tion of these defects with respect to the junction boundary appears to be p articularly important. Elimination or reduction of fluctuations in relative flux magnitudes or substrate temperature, more likely during multi-composi tion layer growth, yielded films with significantly lower defect concentrat ions.