Amorphous/microcrystalline silicon superlattices - the chance to control isotropy and other transport properties

Preparation of amorphous silicon/microcrystalline silicon superlattices all owed us a systematic study of transition from isotropic amorphous silicon t o microcrystalline silicon with anisotropic (columnar) microstructure. The fact that just a few nm of amorphous interlayers are sufficient to interrup t columnar growth of crystallites is reflected in a clearly demonstrated is otropy of transport properties of all superlattice samples. Values of dark conductivity and diffusion length as well as grain size vary with changing crystallinity and so we can tailor the properties of the resulting material by adjusting thicknesses of amorphous and microcrystalline layers repeated to achieve a total desired thickness. Properly selected design of superlat tice can lead to transport properties more suitable for solar cells than wi th pure microcrystalline silicon. (C) 2001 American Institute of Physics.