The self-diffusion of Ga in undoped, Si-doped and Be-doped 71GaAs/natGaAs heterostructures was investigated between 736 and 1050C (table 2). The concentration profiles of the Ga isotopes, as measured using secondary ion mass spectrometry, revealed retarded or enhanced self-diffusion in p-type and n-type samples, respectively. A detailed analysis of the doping dependence of the Ga self-diffusion included the compensation of Si donors by negatively charged vacancies. This showed that one native defect, which was presumed to be a vacancy on the Ga sub-lattice, in the neutral, singly- and doubly-negatively charged states, governed self-diffusion. No significant contribution arising from the triply-negatively charged Ga vacancy was detected. Thermal equilibrium concentrations and transport coefficients for Ga vacancies in various charge states were calculated for various doping conditions, while taking account of the vacancy-related energy levels and the thermal equilibrium concentration of neutral vacancies; as deduced from the present self-diffusion data.

Enhanced and Retarded Ga Self-Diffusion in Si- and Be-Doped GaAs Isotope Heterostructures H.Bracht, M.Norseng, E.E.Haller, K.Eberl, M.Cardona: Solid State Communications, 1999, 112[6], 301-14

Table 2

Diffusivity of Ga in GaAs