Carbon doping into GaAs using combined ion beam and molecular beam epitaxy method

Abstract

Carbon (C) doping by combined ion beam and molecular beam epitaxy (CIBMBE) was investigated. In this technique, mass-analyzed C ions (12C+) are accelerated at low energies of 30 to 1000 eV and are irradiated onto growing GaAs substrate. Doping concentration control in CIBMBE can be very stably accomplished by simply adjusting the ion beam current density, which is independent of growth conditions of host materials. Experiments on systematic variation of C+ ion acceleration energy (EC+) indicated that, in the energy range of EC+ <170 eV, net hole concentration (|NA − ND|) increases slightly as EC+ increases. The highest |NA − ND| is obtained at EC+ = 170 eV under the constant C+ ion beam current density. For EC+ > 170 eV, |NA − ND| decreases dramatically with increasing EC+, which can be explained in terms of enhanced sputtering effect. Although no evidence of damages induced by ion irradiation is shown for low EC+ range of ≤170 eV, trace of damages is apparently observed for EC+ > 170 eV.