Transient photocurrents as a spatially resolved probe of carrier transport and defect distributions in silicon thin films

Transient photocurrent spectroscopy (TPC) yields the energetic distribution of localised states in disordered semiconductors from an analysis of the decay of photocurrent with time following a short laser pulse. By comparing results at different laser excitation wavelengths, and hence absorption depths, information on spatial non-uniformities may also be inferred. Here we investigate the use of TPC as a spatial probe with reference to two thin-film silicon systems; amorphous silicon subjected to various light-induced degradation regimes, and microcrystalline silicon grown on a range of ‘seed’ layers. Computer simulation is used to support experimental findings, and to identify sensitivity and resolution limitations.