Effects ofCo60Gamma Irradiation on Epitaxial GaAs Laser Diodes

Abstract

The characteristics of defects introduced in epitaxial GaAs by room-temperature ${\mathrm{Co}}^{60}$ irradiation have been studied by observing the degradation of light emission from GaAs laser diodes. The luminescence degradation is indicative of a decrease in electron lifetime in the $p$-type region brought about by the introduction of nonradiative recombination centers. These defects anneal in a single stage centered at 237°C. Isothermal-annealing studies show that the defects anneal by a first-order kinetic process with an activation energy of 1.7 eV and a preexponential factor of ${10}^{13}$ ${\sec }^{-1\mathrm{}}$. The annealing properties of the defect suggest that it is a complex whose dissociation is the limiting step in the recovery process. The defects can also anneal at temperatures as low as 76°K under the influence of a strong forward bias. A dc forward bias at 2.2×${10}^2$ A/${\mathrm{cm}}^2$ at room temperature for 1 h produces complete recovery of the light intensity. The possibility of annealing due to heating while under strong forward bias has been considered and does not appear to be responsible for the bias annealing. Rather, the forward-bias-induced recovery is thought to be due to an increase in the probability of annihilation because of a change in charge state of the defect complex following capture of a minority carrier. The various aspects of forward-bias annealing observed in this study can be explained by this model. On the basis of the above results, the complex has been tentatively identified as consisting of an impurity and an As interstitial.