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

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 (E_C+) indicated that, in the energy range of E_C+<170 eV, net hole concentration (|N_A-N_D|) increases slightly as E_C+ increases. The highest |N_A-N_D| is obtained at E_C+ = 170 eV under the constant C⁺ ion beam current density. For E_C+>170 eV, |N_A-N_D| decreases dramatically with increasing E_C+, which can be explained in terms of enhanced sputtering effect. Although no evidence of damages induced by ion irradiation is shown for low E_C+ range of ≤170 eV, trace of damages is apparently observed for E_C+>170 eV.