Optically detected photocarrier transport in amorphous silicon: a review

Measurements of photocarrier transport in hydrogenated amorphous silicon, a-Si:H, based on optical techniques are reviewed. Picosecond domain measurements on multilayer and p-i-n diode structures are described as representative of the use of structural inhomogeneities to establish the distance scale of the transport. Measurements using diffraction by photoinduced gratings are described as representative of the use of photoinduced inhomogeneities. The relative effects of thermal and photocarrier gratings upon the diffraction measurements are discussed. It is suggested that photocarrier grating measurements can be re-interpreted to yield the band mobility for holes in a-Si:H, and the value of 0.2 cm²/V s is obtained near room temperature.