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

The diffusion of deuterium (H-2) in epitaxial 4H-SiC layers with buried hig hly Al-acceptor doped regions has been studied by secondary ion mass spectr ometry. H-2 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 H-2 in the high doped layers was observed. To explain the accumulation kinetics, a model is proposed where positively cha rged H-2 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 ot her semiconductors as well, since hydrogen is a common impurity present at high concentrations in many semiconductors.