Kinetic influences on void formation in epitaxially regrown GaAs-Based PCSELs

Abstract

We report an investigation into the formation of crystallographic voids during the metalorganic vapour phase epitaxial regrowth of GaAs photonic crystal structures. We employ a combination of cross-sectional scanning electron microscopy and scanning transmission electron microscopy to study structures regrown with AlAs, AlGaAs and GaAs. The change in regrowth material allows the effect of adatom diffusion kinetics on the void structure to be assessed. Whilst complete grating infill is observed for GaAs, void formation is promoted for Al-containing materials, with void size increasing with Al mole fraction, in line with reduced adatom mobility. In the case of both AlAs and AlGaAs-regrown structures, a degree of asymmetry is observed in the shape of the voids within the plane of the photonic crystal. These differences are attributed to variations in group-III adatom surface mobility and the polarities of high-index crystal planes along orthogonal crystal directions. Two growth regimes of stable and dynamic faceting are observed in cross-sections containing crystal planes with A- and B-type polarities, respectively.