Low-temperature epitaxy for thin-film silicon solar cells by ECRCVD-structural and electronic properties

The homo-epitaxial growth of crystalline Si films at low temperatures by electron-cyclotron resonance chemical-vapor deposition is studied. The presence of boron in the process is found to impede the crystal growth and facilitates the formation of extended defects, which can be made visible by defect etching. The analysis of the resulting etch pits by scanning electron microscopy reveals a high density of structural defects like dislocations and stacking faults. A correlation between the density of a pyramid-shaped etch pit and the photoluminescence spectra is discussed. The density of this etch pit was found to depend on substrate temperature and boron concentration. First solar cell results with an epitaxial grown boron-doped absorber layer are presented.