Simple method for preparing hydrogenated amorphous silicon films by chemical vapor deposition at atmospheric pressure

An inexpensive one-step method is presented for fabricating hydrogenated amorphous silicon (a-Si:H) films with good photovoltaic properties using chemical vapor deposition (CVD) from a mixture of polysilanes, SinH2n+2, in hydrogen at atmospheric pressure. This gas mixture is generated by a simple chemical reaction and used immediately in the CVD process. Thus, the highly flammable polysilanes need not be handled, distilled, stored, or transported. The conditions necessary for high (about 10%) hydrogen incorporation are explained. The method requires no expensive vacuum or electrical equipment and permits very high deposition rates (50–100 Å/s). It is shown that the growth rate of the film is determined by the gas-phase chemistry and not the surface chemistry. In addition a new, safe, and economical technique for phosphorus doping is described.