Positron Mobility Measurements and Their Relevance to Defect and Impurity Studies in Semiconductors and Insulators

Positron mobility measurements and their relevance to the study of defects and impurities in semiconductors and insulators are discussed. Since the short lifetime of the positron in condensed matter renders conventional mobility techniques unsuitable, positron mobility measurements rely on the observation of annihilation photons and of vacuum emission. Measurements utilising Doppler shift, angular correlation, profile shift and diffusion to surfaces are surveyed. New methods which observe the electric field drift of positrons by lifetime spectroscopy or vacuum emission are discussed. Lifetime measurements in Fe doped InP give a positron mobility, μ+ = (15 ± 5) cm2 V−1 s−1 at 77 K.