A simple tool for quality evaluation of the microcrystalline silicon prepared at high growth rate

Silicon thin films were grown by plasma enhanced chemical vapor deposition at high-pressure (700 Pa), high-power (4- W/cm2) depletion regime using multi-hole cathode. Series of samples were deposited by varying hydrogen/silane ratio or plasma power to study evolution of film structure and transport properties near a-Si:H/μc-Si:H transition. We suggest a simple “μc-Si:H layer quality factor” based on the ratio of subgap optical absorption α (1.4 eV)/α (1 eV) measured by constant photocurrent method. This ratio correlates well with the values of ambipolar diffusion lengths measured by surface photovoltage method perpendicularly to the substrate, i.e., in the direction of the collection of the photogenerated carriers in solar cells.