The interdiffusion of a multiple quantum-well sample, due to a thin source of vacancies, was used as a probe for the simultaneous measurement of the interdiffusion coefficient, the diffusivity of group-III vacancies and the background concentration of these vacancies. It was shown that interdiffusion at all temperatures was governed by a constant background concentration of vacancies, and that this concentration was equal to that of the vacancies in the substrate. The measured vacancy concentration was about 2 x 1017/cm3. This showed that the vacancy concentrations were not in thermal equilibrium, contrary to the usual assumption. It instead had a value which was frozen in; probably at the growth temperature. It was shown that the activation energy for the intermixing of InGaAs and GaAs was governed only by the activation energy for vacancy diffusion, which was estimated to have a value of 3.4eV.

O.M.Khreis, W.P.Gillin, K.P.Homewood: Physical Review B, 1997, 55[23], 15813-8