Electric-field-assisted migration and accumulation of hydrogen in silicon carbide

The diffusion of deuterium ${(}^2\mathrm{H})$ in epitaxial $4H-\mathrm{S}\mathrm{i}\mathrm{C}$ layers with buried highly Al-acceptor doped regions has been studied by secondary ion mass spectrometry. ${}^2\mathrm{H}$ was introduced in the near surface region by the use of 20-keV implantation after which the samples were thermally annealed. As a result, an anomalous accumulation of ${}^2\mathrm{H}$ in the high doped layers was observed. To explain the accumulation kinetics, a model is proposed where positively charged ${}^2\mathrm{H}$ ions are driven into the high doped layer and become trapped there by the strong electric field at the edges. This effect is important for other semiconductors as well, since hydrogen is a common impurity present at high concentrations in many semiconductors.