Strong Thickness Dependence of Photoelectronic Properties in Hydrogenated Amorphous Silicon

ABSTRACTMany of the photoelectronic properties of a-Si:H, including photoconductivity and ambipolar diffusion length, were observed to deteriorate rapidly with decreasing film thickness. Calculations show that the thickness dependence can be attributed mainly to the effect of surface recombination. In fact, any surface recombination velocity above 100 cm/s will result in an equally good fit to the experimental data. We conclude that the intrinsic photoelectronic properties of bulk a-Si:H and other related materials can be measured only on thick samples (≥1μm) and by using uniformly absorbing light (at long wavelengths).