The diffusion behavior of host and other atoms in plasma-enhanced chemical vapor deposited layers was studied. It was found that the group-III elements (In, Ga) diffused very quickly at annealing temperatures of between 400 and 600C. The mobilization of these species by OH groups was proposed. The occurrence of As diffusion could be observed only in the case of semiconductor samples which had been etched in an H2SO4 solution before SiO2 deposition. An As-rich interface layer which was produced by this etchant was assumed to act as an exhausting source for mobile As-O complexes. The InGaAs host atoms could be detected, at concentrations of up to about 1018/cm3, in secondary-ion mass spectroscopic studies of SiO2 films after annealing. Their effective diffusion coefficients were estimated to be between 10-15 and 10-13cm2/s within the temperature range which was investigated. Activation energies of about 0.6eV (In), 0.3eV (Ga) and 0.8eV (As) were derived. The out-diffusion of In and Ga was associated with the occurrence of 2 new peaks in the photoluminescence spectra of the InGaAs layers. Binding energies of about 0.011 and 0.018eV, respectively, were deduced. The ability of plasma-enhanced chemical vapor deposited SiO2 layers to act as a diffusion mask during Zn or Cd acceptor diffusion at 500 and 600C was confirmed.

P.Ambrée, K.Wandel: Journal of Applied Physics, 1994, 76[2], 880-6