IDENTIFICATION AND QUANTIFICATION OF DEFECTS IN HIGHLY SI-DOPED GAAS BY POSITRON-ANNIHILATION AND SCANNING-TUNNELING-MICROSCOPY

Defects in highly Si-doped GaAs were identified and their concentratio n determined by combining positron lifetime spectroscopy with scanning tunneling microscopy. We observed with increasing Si-doping concentra tion an increasing concentration of a deep positron trap identified as Si-Ga-donor-Ga-vacancy complex. The concentration of shallow positron traps increased with the Si concentration too. The shallow traps are found to be Si-As acceptors and Si clusters.