Gallium Diffusions into Silicon and Boron-Doped Silicon

Abstract

Radiochemical techniques were used to measure the 72Ga distribution profiles resulting from gallium diffusions into intrinsic silicon and into boron-prediffused extrinsic silicon. Gallium diffusions were conducted from 900 to 1050 °C. Gallium diffusivity in intrinsic silicon is found to be well described by the expression Dint =60 exp(−3.89 eV/kT) cm2/sec and in heavily boron-doped extrinsic silicon by the relation Dext ≃ 0.008(−2.49eV/kT) cm2/sec. The observed increase in Ga diffusivity with hole concentration is explained by means of a generalized monovacancy diffusion model, in which the diffusion of ionized substitutional impurities in silicon is assumed to be controlled primarily by the concentration vacancies of the opposite charge type.