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 °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 μm. The result shows that the dislocation-accelerated diffusion of Si impurities is considerable and the inclusion of a thick buffer layer (−3 μm) is not sufficient for preventing the diffusion of the impurities into a device-active region near the GaAs surface if high temperature (>800 °C) processing is involved.