Luminescence of a-screw dislocations in low-ohmic GaN

Abstract

Straight segments of a-screw dislocations introduced by indentation or scratching of the basal (0001) or prismatic (01-10) surfaces of intentionally undoped low-ohmic GaN were found to radiate a doublet of narrow luminescent lines in the spectral region at about 3.1 - 3.2 eV. The components of the doublet were separated by about ∼30 meV and accompanied with LO-phonon replicas. The intensity of the dislocation-related luminescence was significantly higher than that of free exciton in dislocation-free regions indicating a giant oscillator strength of dislocation-related luminescence optical transition that was proposed to occur between the electron states of the stacking fault and the hole states of the bounded partials in the core of the dissociated screw dislocation.