CARBON DOPING INTO GAAS USING COMBINED ION-BEAM AND MOLECULAR-BEAM EPITAXY METHOD

Carbon (C) doping by combined ion beam and molecular beam epitaxy (CIB MBE) was investigated. In this technique, mass-analyzed C ions (C-12()) are accelerated at low energies of 30 to 1000 eV and are irradiated onto growing GaAs substrate. Doping concentration control in CIBMBE c an be very stably accomplished by simply adjusting the ion beam curren t 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 co ncentration (\N-A-N-D\) increases slightly as E(C+) increases. The hig hest \N-A-N-D\ is obtained at E(C+)=170 eV under the constant C+ ion b eam current density. For E(C+) > 170 eV, \N-A-N-D\ decreases dramatica lly with increasing E(C+), which can be explained in terms of enhanced sputtering effect. Although no evidence of damages induced by ion irr adiation is shown for low E(C+) range of less than or equal to 170 eV, trace of damages is apparently observed for E(C+) 170 eV.