Study on Defects in GaAs by means of Positron Annihilation

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1. Study of LEC-GaAs(1) Measurement of positron lifetime and Doppler-broadened annihilation have been performed on electron irradiated LEC-GaAs. Recovery and clustering of electron induced defects were published in Applied Physics A 58,59(1994)(2) Temperature dependence of proton irradiation induced defects were studied using positron annihilation technique. Below 300K the charge state Si doping induced defects were investigated and Gallium vacancies and antisite GaAs were produced after proton irradiation (submitted in Applied Phys A).2. Production of slow positron beam using A VF Cyclotron.(1) Construction of System for production of slow positron beam. System has been modified for high quality slow positron beam and low background.(2) Several targets such as boron nitride (BN), Carbon, Si_3N_4 and, NaF were used for beta_+ decay reaction. For BN slow positron intensity of 1.4 X 10^4/sec was obtained.