Vacancy-type defects in molecular beam epitaxy low temperature grown GaAs, a positron beam lifetime study

Positron beam lifetime spectroscopy has been utilized to study the depth distribution of vacancy-type defects in molecular beam epitaxy GaAs grown at low temperature. Lifetime spectra were measured as a function of positron energy. From the analysis of the positron lifetime in as-grown and annealed low temperature grown GaAs, the concentrations of Ga monovacancies and voids are estimated. Our results show that in an as-grown sample the Ga monovacancy concentration is > 3 x 10(18) cm(-3). It is also known that vacancy-cluster concentration in an annealed sample exceeds 10(18) cm(-3) with a nonuniform spatial distribution. (C) 1996 American Institute of Physics.