As_Ga antisite defects formed during plastic deformation of GaAs are identified by electron paramagnetic resonance (EPR) measurements. From photo‐EPR results it can be concluded that the two levels of this double donor are located near E_c −0.75 eV and E_v +0.5 eV. These values are coincident with the Fermi level pinning energies at Schottky barriers. The upper level can be related to the ’’main electron trap’’ EL2 in GaAs. Photoluminescence experiments before and after thermal annealing suggest that As_Ga defects reduce the near band edge luminescence efficiency. A dislocation climb model is presented which is able to explain As_Ga formation during dislocation movement. The production of As_Ga antisites during dislocation motion under injection conditions in light emitting devices may thus be connected with degradation of the light output.

A new electron trap, labeled ED1, with an activation energy of 0.68 eV has been found to appear in the deep‐level transient spectroscopy spectrum of n‐type GaAs crystals as a result of their plastic deformation at 400 °C. The trap has been systematically investigated taking into account broadening of its energy level. The trap concentration was proportional to the dislocation density and not affected by the post‐deformation annealing at 500 °C. The concentration of electrons captured at the trap was found to depend logarithmically on the duration time of the filling pulse and an acceptor character of the trap was established. The results are analyzed in a model involving barrier‐limited capture rate, and it is concluded that the ED1 traps are most probably located in the dislocation core. Possible types of dislocations responsible for the traps are discussed.

We study radiative and nonradiative recombination at individual dislocations in GaN by cathodoluminescence performed in a transmission electron microscope. The dislocations are produced by indentation of dislocation free single crystals and have a-type Burgers vectors (b=1/3〈112̄0〉). They are aligned along 〈112̄0〉 directions in the basal plane. Our direct correlation between structural and optical properties on a microscopic scale yields two main results: (i) 60°-basal plane dislocations show radiative recombination at 2.9 eV; (ii) screw-type basal plane dislocations act as nonradiative recombination centers. We explain the nonradiative recombination by splitting this dislocation into 30° partials that have dangling bonds in the core. The dissociation width of these dislocations is <2 nm.

Structural and optical properties of freshly created and in-grown dislocations in GaN single crystal are investigated by Raman and cathodoluminescence (CL) microscopy. The introduction of a high density of dislocations by micro-indentation is accompanied by the generation of intrinsic point defects. A high amount of ${\mathrm{V}}_{\mathrm{Ga}}$ –impurity complexes is responsible for the decrease in the free electron concentration and the enhanced yellow luminescence around the indentation. A compressive stress induced by deformation is revealed by Raman scattering and CL. In-grown dislocations are decorated with a point defect atmosphere, leading to a reduction in the free carrier concentration around the dislocation.