VIBRONIC LEVELS OF THE EL2 CENTER UNDER UNIAXIAL-STRESS

We study the vibronic levels of the arsenic antisite defect in GaAs and the optical properties associated with the A1-->T2 transition of the As(Ga) defect. In our model we include both the Jahn-Teller effect on the T2-degenerate states and the effect of a uniaxial stress applied along several crystal directions; the coupled system of electron-vibrational states is handled with the recursion method. With a coupling with a phonon mode of symmetry tau2 we have calculated the features of the transition line at 8378 cm-1 and its replicas; relationships with available experimental data and microscopic models are discussed.