Effects of dislocation density on the properties of liquid phase epitaxial GaAs

Abstract

A study has been made of the effect of dislocation density on the properties of p-type GaAs (Ge-doped, p = 1 × 1019 cm−3) grown homoepitaxially on GaAs and heteroepitaxially on GaP. It has been found that dislocation densities > 5 × 106 cm−2 reduce the minority-carrier diffusion length in the p-type material and, consistent with this reduction, degrade the junction electroluminescence and p-layer photoluminescence. At high dislocation densities (> 5 × 106 cm−2), it is also found that subgrains form in the GaAs epitaxial layers grown either heteroepitaxially on GaP or homoepitaxially on GaAs. It is surmised that the dislocations polygonize during growth to form subgrain boundaries rather than form due to nucleation at the substrate. Finally, the results indicate that the electron diffusion length is limited to the average dislocation spacing with the dislocations acting as nonradiative recombination centers for electrons.