Annealing Characteristics Of Low Temperature Grown GaAs:Be

<jats:title>ABSTRACT</jats:title><jats:p>We have studied the annealing characteristics of acceptor doped GaAs:Be grown at Low substrate Temperatures (300°C) by Molecular Beam Epitaxy (LTMBE). The Be was introduced in a range of concentrations from 10<jats:sup>16</jats:sup> –10<jats:sup>19</jats:sup> cm<jats:sup>−3</jats:sup>. As-grown material was found to be n-type even up to the highest Be concentration of 10<jats:sup>19</jats:sup> cm<jats:sup>−3</jats:sup> although Raman spectroscopy of the Be local vibrational mode indicates that the majority of the Be impurities are substitutional. We propose that Be acceptors are rendered inactive by the high concentration of As<jats:sub>Ga</jats:sub>-related native donor defects present. Results of slow positron annihilation studies indicate an excess concentration of V<jats:sub>Ga</jats:sub> in LTMBE layers over bulk grown crystals. A distinct annealing stage at 500°C, similar to irradiation damaged and plastically deformed GaAs, marks a rapid decrease in the As<jats:sub>Ga</jats:sub> defect concentration. A second annealing stage at 800°C corresponds to the activation of Be acceptors. Analysis of isothermal annealing kinetics for the removal of As<jats:sub>Ga</jats:sub>-related defects gives an activation energy of 1.7 ±0.3 eV. We model the defect removal mechanism with the V<jats:sub>Ga</jats:sub> assisted diffusion of AS<jats:sub>Ga</jats:sub> to As precipitates.</jats:p>