Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

Heterojunctions made of hydrogenated amorphous silicon (a-Si : H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n)a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p)a-Si:H/(n)c-Si structures implies a quite large valence band offset (E-V(c-Si)-E-V(a-Si:H) > 0.25 eV). (C) 2010 American Institute of Physics. [doi:10.1063/1.3525166]