ABSTRACTThree examples pertaining to the influence of heavy doping on the microscopic perfection of as-grown InP crystals, thermal decomposition of InP crystals and epi-layers and optically induced degradation of InGaAsP epi-layers have been chosen to delineate some of the correlations observed between microstructure and properties in these materials. It is shown that the macroscopic perfection can be significantly improved by highly doping with Zn, S, and Se. However, in the case of Zn, not all of the dopant atoms are in solid solution and some of them have clustered to form precipitates, whereas these features are not seen in highly S- and Se-doped crystals.Thermal decomposition of epi-layers introduces areas which appear dark in a photoluminescence scan. It is argued that these regions evolve due to the out diffusion of P. In addition, when InP epi-layers are grown on thermally-decomposed substrates, dislocation density in the epi-layers is higher than that in the substrate. Arguments have been developed to rationalize these observations.Non-luminescent regions develop in InGaAsP epilayers by optical pumping. These areas are associated with dislocation clusters which appear to evolve by glide of the existing dislocations.
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