Atomic structure and electronic properties of c-Si/a-Si:H heterointerfaces

The atomic structure and electronic properties of crystalline-amorphous interfaces in silicon heterojunction solar cells are investigated by high-resolution transmission electron microscopy, atomic-resolution Z-contrast imaging, and electron energy-loss spectroscopy. With these combined techniques, we directly observe abrupt and flat transition from crystalline Si to hydrogenated amorphous Si at the interface of Si heterojunction solar cells. We find that high-quality hydrogenated amorphous Si layers can be grown abruptly by hot-wire chemical vapor deposition on 200 degrees C (100) Si substrates after a two-step pretreatment of the substrate, comprised of exposure to hot-wire decomposed H-2-diluted NH3 followed by atomic H etching.