Identification of theBiGaheteroantisite defect in GaAs:Bi

GaAs lightly doped with the heaviest group-V atom, bismuth (Bi), has been studied by conventional electron-spin resonance (ESR) and by ESR detected via the magnetic-circular-dichroism (MCD) absorption. A new Bi-related sharp-line MCD band has been observed on which two MCD-ESR lines have been discovered. They are shown to arise from the singly ionized ${\mathrm{Bi}}_{\mathrm{Ga}}$ double donor. Most remarkably, a substantial fraction, about 10%, of the total Bi content is found to occupy the Ga site. The ${\mathrm{Bi}}_{\mathrm{Ga}}$ MCD absorption band is tentatively assigned to an exciton deeply bound to the singly ionized double donor ${\mathrm{Bi}}_{\mathrm{Ga}}^{+}$.