Optical properties of fresh dislocations in GaN

Optical properties of fresh dislocations, (a/3)[1 1 (2) over bar 0]-type edge dislocations on the (1 (1) over bar 0 0) prismatic plane, introduced into GaN by plastic deformation at elevated temperatures were investigated by photoluminescence and optical absorption measurements. Plastic deformation acts as an effective passivation, leading to remarkable reduction of near-band-edge photoluminescence intensity centered at 3.48 eV and noticeable red-shift of the optical absorption edge. In a model of the Franz-Keldysh effect, the induced edge dislocations posses nonradiative trap sites around 3e/c along their core, resulting in the reduction of free-carrier concentration. Also, the induced dislocations give rise to some luminescence peaks in the energy range 1.7-2.4 eV, differing from the yellow luminescence, which implies the formation of radiative recombination centers by the dislocations. (C) 2010 Elsevier B.V. All rights reserved.