Experimental and numerical studies of Ar-laser-assisted Si doping of GaAs with SiBr4 by chemical beam epitaxy

Doping results from Ar⁺-laser-assisted chemical beam epitaxy with triethylgallium, tris(dimethylamino) arsenic and silicon tetrabromide as group-III, group-V and dopant precursors, respectively, are reported. Enhancements in the n-type doping concentration are observed with laser irradiation in the investigated substrate-temperature range 390 – 500°C. With a 300 W/cm² irradiation power density, an increase in the carrier concentration by 70 times is obtained at 390°C substrate temperature. A numerical model developed by us for epitaxial growth and doping with the above precursors is used to assess the contribution of laser-induced thermal heating to the observed doping increase. A reaction scheme for photo-induced decomposition of physisorbed silicon tetrabromide is proposed. A kinetic rate equation for the photolysis is derived and used to estimate the absorption cross section required to reproduce the observed concentration enhancements resulted from laser irradiation. The possibility is established that dramatic increases in carrier concentration at low growth temperatures are due to photolysis of physisorbed silicon tetrabromide.