Electrical, Luminescence and SIMS Characterization of Carbon Implanted Vapor Phase Epitaxial Gallium-Arsenide

The electrical, luminescence and mass distribution properties of carbon implanted VPE GaAs have been analyzed. Room temperature Hall measurements and low temperature photoluminescence (PL), each combined with chemical etching, and SIMS experiments were performed on VPE GaAs which had been implanted with 120 keV carbon atoms in doses ranging from 1 x 10('13) cm('-2) to 1 x 10('15) cm('-2). Useful data was obtained for carbon concentrations of 1 x 10('16) cm('-3) to 3 x 10('19) cm('-3). The electrical and PL etch data independently identify a saturation effect for substitutional carbon acceptors at a concentration of approximately 3 x 10('17) cm('-3). For lower concentrations, the carbon goes strongly to As sites and acts as an acceptor, while for higher concentrations the carbon goes to electrically and optically inactive sites, identified as precipitated carbon clusters. The PL etch data show the effect of carbon concentration on the 1.4935 eV carbon acceptor line above and below the saturation concentration of 3 x 10('17) cm('-3). Several new luminescence lines are also reported. Defect related excitons appear at 1.5102, 1.5083 and 1.5020 eV and their intensities are strongly enhanced by the presence of carbon. A new vacancy complex has been identified at 1.384 eV which has tentatively been associated with Si acceptors. The overall conclusion is that, for carbon concentrations above approximately 3 x 10('17) cm('-3), the excess carbon will not go substitutional and that for carbon concentrations less than 3 x 10('17) cm('-3), the carbon will reside predominately on As sites as an acceptor, unlike the amphoteric behavior of other Group IVA impurities in GaAs.