A novel technique for S-doping was demonstrated. The surface was treated with (NH4)2Sx solution before annealing by using furnace or rapid thermal processing. The S atoms which were adsorbed at the surface during the (NH4)2Sx treatment diffused into the bulk during annealing. The S diffusion profiles after either annealing treatment were concave from the surface. The S diffusion constants, as determined using the Boltzmann-Matano technique, increased with decreasing S concentration below the surface. This suggested that immobile S-donors, SAs+, formed at the near surface, interacted with a Ga divacancy, and resulted in the production of mobile As interstitials, IAs. The latter moved rapidly towards the interior and kicked-out the SAs+ donors so as produce a fast-diffusing species of interstitial S atoms. The diffusion coefficient of S was deduced to be 2.5 x 10-14cm2/s at 840C and 5 x 10-12cm2/s at 900C.

Sulfur doping of GaAs with (NH4)2Sx solution J.L.Lee: Journal of Applied Physics, 1999, 85[2], 807-11