DISLOCATION-ACCELERATED DIFFUSION OF SI IN DELTA-DOPED GAAS GROWN ON SILICON SUBSTRATES BY METALORGANIC CHEMICAL VAPOR-DEPOSITION

Abstract

Capacitance-voltage (C-V) profiling of delta-doped GaAs layers grown by metalorganic chemical vapor deposition on Si substrates has been employed to demonstrate a dislocation-accelerated diffusion of Si impurities initially confined in the delta-doped sheets. A close correlation between dislocation densities in the epitaxial layers and the diffusion coefficients obtained from C-V analyses is established. After rapid thermal annealing at 800, 900, 950, and 1000-degrees-C for 7 s, the temperature dependence of the diffusion coefficient is found to be D-30 exp( -3.4 eV/kT) for a delta-doped GaAs-on-Si with a relatively thick buffer layer of 3.3-mu-m. The result shows that the dislocation-accelerated diffusion of Si impurities is considerable and the inclusion of a thick buffer layer ( -3-mu-m) is not sufficient for preventing the diffusion of the impurities into a device-active region near the GaAs surface if high temperature (> 800-degrees-C) processing is involved.