Optical and electrical properties of dislocations in plastically deformed GaN

Optical and electrical properties of fresh dislocations in GaN bulk crystals deformed plastically at elevated temperatures were reviewed. A dislocation band model was proposed. The fresh dislocations of (a/3) [12¯10]-type edge dislocations on the (101¯0) prismatic plane induced several photoluminescence peaks at around 1.8, 1.9 and 2.4 eV, which implies the formation of radiative recombination centers of the dislocations. Simultaneously, near-band-edge (3.48 eV) photoluminescence intensity decreased remarkably for a high-density of non-radiative recombination centers originating in deformation-induced abundant Ga-vacancy related clusters. The intensity variation of yellow luminescence with plastic deformation and subsequent annealing did not relate to the native property of dislocations. Variation of optical absorption dependent on the strain in plastically deformed GaN was understood in a model of the Franz-Keldysh effect by the electric fields associated with charged dislocations (~5.8 e/nm). Scanning spreading resistance microscopic images showed many spots with high conductivity around the induced dislocations, showing electrical conduction along dislocations according to the Frenkel-Poole mechanism.