Abstract
Earlier results determined the diffusion coefficients of Ga in both amorphous and crystalline silicon. Computer modeling shows that growth of silicon n-i-p-i superlattices with high doping and narrow layer width by either conventional molecular-beam epitaxy or solid-phase epitaxy leads to smearing of the Ga profile because of its relatively large diffusion coefficients in both the amorphous and crystalline states. A method of sequential amorphous deposition and crystallization is presented that minimizes the Ga diffusion. Superlattices with Ga and Sb doping of ≊5×1018 cm−3 and layer thickness of ≊25 nm are shown. The crystal surface after all regrowths produces very sharp low-energy electron diffraction patterns, and Auger electron spectroscopy shows the numerous growth interfaces to be clean to better than 1% of a monolayer of O or C.