Irradiation-induced defects in GaAs

From a discussion of the experimental results concerning defect creation (versus the energy of irradiation, temperature, doping concentration, nature of the material, crystalline orientation) and annealing (versus doping concentration, carrier injection), it is concluded that the defects produced in n- and p-type GaAs by electron irradiation consist in a distribution of vacancy-interstitial pairs in the As sublattice. The vacancy-interstitial pairs in the Ga sublattice recombine immediately after their creation. The mobility of the As interstitial, which can be induced by hole injection in the case of irradiation with high fluxes, explains the formation of antisites AsGa by exchange with donor impurities on Ga sites and of few complexes following irradiations at high fluences. The existence of several types of pairs explains the occurrence of the numerous electron and hole traps observed. The electrical and optical characteristics of the electron traps are consistent with the existence of a strong-electron-lattice coupling which can be evaluated semiquantitatively.