APPLICATION OF REAL-TIME SPECTROSCOPIC ELLIPSOMETRY FOR CHARACTERIZING THE STRUCTURE AND OPTICAL PROPERTIES OF MICROCRYSTALLINE COMPONENT LAYERS OF AMORPHOUS SEMICONDUCTOR SOLAR CELLS

摘要

Over the past few years, we have applied real-time spectroscopic ellipsometry (RTSE) to probe hydrogenated amorphous silicon (a-Si:H)-based solar cell fabrication on the research scale. From RTSE measurements, the microstructural development of the component layers of the cell can be characterized with sub-monolayer sensitivity, including the time evolution of (i) the bulk layer thicknesses which provide the deposition rates, and (ii) the surface roughness layer thicknesses which provide insights into precursor surface diffusion. In the same analysis, RTSE also yields the optical properties of the growing films, including the dielectric functions and optical gaps. Results reported earlier have been confined to p-i-n and n-i-p cells consisting solely of amorphous layers, because such layers are found to grow homogeneously, making data analysis relatively straightforward. In this study, we report the first results of an analysis of RTSE data collected during the deposition of an n-type microcrystalline silicon (mu c-Si:H) component layer in an a-Si:II p-i-n solar cell. Such an analysis is more difficult owing to (i) the modification of the underlying i-layer by the H-2-rich plasma used in doped mu c-Si:H growth and (ii) the more complex morphological development of mu c-Si:H, including surface roughening during growth. [References: 7]