A STUDY OF SI OUTDIFFUSION FROM PREDOPED GAAS

Experiments have been conducted to study the Si outdiffusion behavior in GaAs using predoped samples. The results showed that the Si diffusi vity values are dependent on the As4 vapor-phase pressure in the ambie nt, and on the electron concentration in the crystal. It is concluded from these results that, in GaAs, diffusion of the Si donor species oc cupying Ga sites Si(Ga)+ is governed by the triply negatively charged Ga vacancies, V(Ga)3-. The present V(Ga)3--dominated Si(Ga)+ outdiffus ion diffusivity values are, however, larger than those obtained under Si indiffusion conditions by many orders of magnitude. A tentative exp lanation of this large difference is given in terms of an undersaturat ion of V(Ga)3- in intrinsic GaAs during indiffusion experiments and of a supersaturation of V(Ga)3- developed during the outdiffusion of Si from n-type, Si-doped GaAs.