Positron annihilation and scanning tunneling microscopy used ot characterise defects in highly si-doped GaAs

摘要

Positron annihilation and scanning tunneling microscopy were combined to characterise defects in highly silicon doped GaAs. An increaasing density of monovacancies was observed by positron lifetime spectroscopy with increasing Si-doping concentration .These vacancies were identified by STm as Si sub Ga-V sub Ga complexes. The ocncentration of shallow positron traps increase with the Si ocncentratio too. The shalow trpas are identified by STm as Si sub As acceptors. The STm results suggest that positron trappingat shallow traps can also be related to small si clusters. The defects are thermally stable at least up to 880 degree. We demonstrate that the combination of positron annihilation and scanning tunneling microscopy is a powerful tool to obtain microscopic data on the concentration and nature of point defects.