The intermixing of AlGaAs-based interfaces was enhanced by capping wafers with a layer of SiO2. By assuming that this enhancement resulted from the introduction of additional Ga vacancies into the sample, it was possible to estimate the temperature-dependent equilibrium Ga vacancy diffusivity. Experiments were performed in which SiO2-capped quantum-well samples were annealed at temperatures ranging from 800 to 1025C. The calculated photoluminescence shifts were compared with the measured spectra and a relationship, for the Ga vacancy diffusivity, of the form:

D (cm2/s) = 0.962 exp[-2.72(eV)/kT]

(table 10) was obtained. By using this relationship, the equilibrium Ga vacancy concentration could be estimated via Monte Carlo simulation. The resultant expression was: C (/cm3) = 1.25 x 1031 exp[-3.28(eV)/kT].

K.B.Kahen, D.L.Peterson, G.Rajeswaran, D.J.Lawrence: Applied Physics Letters, 1989, 55[7], 651-3

Table 10

Diffusivity of Ga Vacancies in GaAlAs