Measurement of transversal ambipolar diffusion coefficient in microcrystalline silicon

Transport properties of microcrystalline silicon (mu c-Si) are analyzed by diffusion-induced time resolved microwave conductivity (DTRMC), a new conta ctless method. Computer simulations show that with this method the ambipola r diffusion coefficient of carriers in the transversal direction, even for thin layers (typically 100 nm), can be determined. Ex situ measurements are made on several samples with various mu c-Si thicknesses deposited in the same conditions. The evolution of transport parameters with layer thickness is correlated with the inhomogeneity of the layer structure detected by el lipsometry. In particular, we demonstrate that the presence of an amorphous interface between the substrate and mu c-Si can be the main limiting facto r of transversal transport. (C) 2000 Elsevier Science B.V. All rights reser ved.