Positron Trapping at Point Defects in Electron-Irradiated GaAs

The effect of irradiation by electron beams of low (j = 5 × 10−3 A/cm2) and high density (j = (1.4 to 1.5) × 103 A/cm2 on Czochralski-grown n-GaAs 〈Te〉 is studied using the positron annihilation technique. Two components τIV = 265 ps and τ2V −320 ps are found in the decay spectrum in initial material and are connected with VGa and divacancies. The intensity of the τIV and τ2V-components in the positron lifetime spectra increases with the fluence and the τ2V-component of the lifetime spectrum has a ADAP Gaussian component with a halfwidth Γ2 = 8.73 mrad. Post-irradiation annealing up to 300 °C reveals the vacancy clusters (τ3 ≈ 420 ps) to be formed as secondary defects. In high-density-electron-beam-irradiated samples vacancy agglomerates (nV ≧ 6) with τ3 ≈ 590 ps-mark appear as the primary defects. The temperature dependence of the position trapping in irradiated samples is deduced. [Russian Text Ignored].

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