Carrier diffusion in microcrystalline silicon studied by the picosecond laser induced grating technique

We report on the picosecond laser induced grating technique applied to hydr ogenated microcrystalline silicon (muc-Si:H) and aimed at studying the phot ocarrier diffusion coefficient D. We have studied a series of three samples having a distinctly different content of the crystalline phase, and the mi crostructure and morphology of which are known in detail. Our results show that the coefficient D scales with the degree of crystallinity of the sampl es, reaching values up to D=9 cm(2) s(-1) close to crystalline silicon. The obtained carrier lifetime (approximate to1 ns) is constant in all measured samples. The extracted diffusion lengths are much greater than the dimensi ons of the microcrystalline grains in the samples. We conclude that small g rain boundaries do not limit substantially the carrier diffusion length in microcrystalline silicon. (C) 2001 American Institute of Physics.