Effects of the Fermi Level on Defects in Be+-Implanted GaAs Studied by a Monoenergetic Positron Beam

Abstract
Vacancy-type defects in 60-keV Be+-implanted GaAs(100) were studied by a monoenergetic positron beam. The depth distribution of vacancy-type defects in an n-type specimen (Si, 1×1016 Si/cm3) was obtained from measurements of Doppler broadening profiles of the positron annihilation as a function of incident positron energy. The dominant defect species was identified as a divacancy from the characteristic value of the line-shape parameter S. These defects, however, could not be observed in the p-type specimen (Zn, 3×1018 Zn/cm3). This fact can be attributed to the recombination of vacancy-type defects and interstitial Ga atoms introduced by the Fermi level effect.