Capacitance-voltage methods were used to profile δ-doped GaAs layers which had been grown on Si substrates via metalorganic chemical vapour deposition. It was found that there was a close correlation between dislocation densities, in the epitaxial layers, and the associated diffusion coefficients. After rapid thermal annealing (800-1000C, 7s), the diffusion data (table 24) could be described by:

D(cm2/s) = 30 exp[-3.4(eV)/kT]

for a relatively thick buffer layer of 0.0033mm. It was concluded that the dislocation-enhanced diffusion of Si impurities was appreciable, and that the inclusion of an 0.003mm buffer layer was insufficient to prevent the diffusion of impurities.

Y.Kim, M.S.Kim, S.K.Min, C.Lee: Journal of Applied Physics, 1991, 69[3], 1355-8

Table 24

Diffusivity of Si in GaAs