Control of crystallinity and orientation of microcrystalline silicon using in situ RHEED observation

In-situ monitoring using reflection high energy electron diffraction (RHEED) and its feedback to control the growth of microcrystalline silicon for higher solar cell performance are demonstrated. With elevating growth temperature, incubation thickness at which nucleation of crystal growth starts to occur decreases, while nucleation density increases, resulting in disruption of columnar growth due to the collision. The [220] preferential growth is most enhanced at a moderate temperature of 250°C, while the incubation thickness at this temperature is rather large. In order to achieve small incubation thickness and highly preferential orientation, a two step growth method has been developed, and as a result, we found that a seeding layer deposited at 430°C and a subsequent layer at 250°C results in highly [220] oriented growth with small incubation thickness