Climb asymmetry in degraded gallium arsenide lasers

Abstract

The dislocation networks associated with 〈100〉 ‘dark-line defects’ in GaAs consist of climb dipoles with an elongation E perpendicular to both the [001] junction-plane normal and the defect Burgers vector. Defining E as a unit vector parallel to the direction of ‘maximum’ elongation, the 〈100〉 networks have been fully analysed and have been found to exhibit an anisotropic growth which reflects the symmetry of the zinc-blende lattice. The polarity of the lattice has been determined and the crystallography of the dipoles identified. The anisotropic climb is accounted for by a difference in the dislocation core structures of opposite-sign parallel dislocations.