  We have prepared light emitting nanocrystalline porous silicon (PS) layers by
electrochemical anodization of crystalline silicon (c-Si) wafer and
characterized the c-Si/PS heterojunctions using temperature dependence of dark
current-voltage (I-V) characteristics. The reverse bias I-V characteristics of
c-Si/PS heterojunctions are found to behave like Schottky junctions where
carrier transport is mainly governed by the carrier generation-recombination in
the depletion region formed on the PS side. Fermi level of c-Si gets pinned to
the defect levels at the interface resulting in ln(I) proportional to V^0.5.
The barrier height in the reverse bias condition is shown to be equal to the
band offset at the conduction band edges. An energy band diagram for the
c-Si/PS heterojunction is proposed.
