Introduction and annealing of defects inn-type gaas following irradiation with electrons and gamma rays

Abstract

The formation of radiation defects in n-type GaAs during irradiation with 28-MeV electrons and Co⁶⁰ gamma rays has been studied as a function of the degree of doping and type of dopant. It has been found that irradiation with electrons generates isolated defects A, B and defect clusters R, while irradiation with Co⁶⁰ gamma rays creates isolated defects B and C. Defect B has been shown to act as a double-charge acceptor with the upper energy level E_c –0.03 ± 0.01 eV and the lower one E ≤ E_c –0.30 eV. The rates of introduction of the defect during irradiation with gamma rays and electrons are 3.10⁻³ cm⁻¹ and 2 cm⁻¹, respectively. Defect C, which is probably also a many-charge defect, contributes mainly to the carrier removal at irradiation with gamma rays. The annealing processes of defects B and C are found to be the first-order reactions with activation energies of 1.5 eV and 1.7 eV and frequency coefficients of 10¹² sec⁻¹ and 10¹³ sec⁻¹, respectively. It has been found that the introduction and annealing of isolated defects is independent of the concentration and the nature of the dopant (Si, Ge, Sn, S, Se, Te). Isolated defects are suggested to be intrinsic structural imperfections or their complexes with residual impurities whose concentrations in all crystals should not be lower than 5^.10¹⁸ cm⁻³.