Dislocations in GaAs17−xPx

Abstract

Dislocations, their origins, and their effects on photoluminescence efficiency have been studied in GaAs1−xPx single crystals grown by vapor phase epitaxy. Dislocations were observed using etch pit, optical-transmission microscopy, and x-ray topography techniques. Two types of dislocations are grown into GaAs1−xPx epitaxial crystals. Near the GaAs (substrate)-GaAs1−xPx interface a high density (>108 cm−2) of pure edge dislocations with axes and Burgers vectors lying in the growth plane was observed. These originate from the lattice parameter mismatch between substrate and epitaxial layer. In the bulk GaAs1−xPx, a high density (∼106 cm−2) of dislocations was observed with 〈211〉 and 〈100〉 directions and Burgers vectors parallel to those of the mismatch dislocations. These dislocations originate from the mismatch dislocations at the substrate-epitaxial layer interface. The effect of dislocations on photoluminescence efficiency was studied by a novel technique. The photoluminescence was excited by focusing a He–Ne laser onto a 20-micron spot on the polished sample surface. The photoluminescence was observed through a microscope at ×400 magnification. It was found that the dislocations grown into the GaAs1−xPx are not intrinsically deleterious to the photoluminescence efficiency; however, in impure material, impurities segregate at dislocations causing a lowering of the luminescence efficiency in a region within one micron of the dislocation core.