Quantitative measurements of recombination enhanced dislocation glide in gallium arsenide

Abstract

Effects of 30-keV electron-beam irradiation on dislocation glide were investigated for α- and β-dislocations in bulk n-GaAs single crystals by cathodoluminescence microscopy using a scanning electron microscope with a bending apparatus in it. At high temperatures above Tc, the electron irradiation has no effect on dislocation velocity v and the temperature dependence v(T) follows an Arrhenius formula v0d exp(−Ed/kT). Below Tc, v(T) under irradiation breaks off the above relation and is enhanced following another Arrhenius formula v0i exp(−Ei/kT). The enhancement effect is completely reversible for individual dislocations. From measurements of irradiation intensity I and stress τ dependences, the dislocation velocity was found to be expressed by a unified formula v=v0d exp[−Ed(τ)/kT ]+v*i(I/I0)0.84 exp{−[Ed(τ)−ΔE]/kT}, which is explained by neither a heating effect nor a charge state effect, but the recombination enhanced defect motion (REDM) mechanism. In view of the REDM mechanism, the ΔE (∼0.7 eV for α-dislocations and ∼1.1 eV for β-dislocations) is related to the energy released upon a nonradiative recombination of generated excess carriers at the dislocations. Based on this postulation, the electronic energy states associated with dislocations are discussed in conjunction with previous, related studies.