Low-temperature positron transport in semi-insulating GaAs

Abstract

Positron diffusion and drift in semi-insulating (SI) GaAs in the temperature range of 50-300 K were studied by the slow-positron beam technique. Both the temperature-dependent positron diffusion coefficient and positron mobility were measured independently using the method reported recently [Y. Y. Shan et al., Phys. Rev. B 54, 1982 (1996)]. The experimental results are consistent with the Einstein relation. The diffusion coefficient and mobility approximately follow D +(T)=9400T -β cm 2 s -1, and μ +(T)=10 8×T -σ cm 2 V -1 s -1, with β=1.5±0.1, and σ=2.5±0.2, respectively in the temperature range of 50-300 K. The results are consistent with scattering from optical-phonon modes as the dominant scattering process for positron transport in GaAs (SI) in this temperature range. No trapped positron states were observed to 50 K.