25. Amorphous and Microcrystalline Silicon

Processes used to grow hydrogenated amorphous silicon (a-Si : H) and microcrystalline silicon (μc-Si : H) from SiH₄ and H₂ ∕ SiH₄ glow discharge plasmas are reviewed. Differences and similarities between growth reactions of a-Si : H and μc-Si : H in a plasma and on a film-growing surface are discussed, and the process of nucleus formation followed by epitaxial-like crystal growth is explained as being unique to μc-Si : H. The application of a reaction used to determine the dangling-bond defect density in the resulting a-Si : H and μc-Si : H films is emphasized, since it can provide clues about how to improve the optoelectronic properties of those materials for device applications, especially thin-film silicon-based solar cells. Material issues related to the realization of low-cost and high-efficiency solar cells are described, and finally recent progress in this area is reviewed.