A novel approach for deposition of device-quality microcrystalline silicon at a high rate using plasma-enhanced chemical vapour deposition has been developed under high-pressure depletion conditions. This method enables us to obtain materials with good crystallinity up to a high deposition rate of 3.8 nm s −1 at around 300˚C. Further improvements in the crystallinity as well as electrical properties have been achieved using a mesh electrode with a hollow-like discharge around the mesh. This hollow mesh method results in a low defect density of 2.6 × 10 16 cm −3 and a volume fraction over 70% at a growth rate of 5.8 nm s −1 . Another beneficial effect of this method was complete suppression of powder formation even at the high deposition pressure. These methods have been applied to solar cells, and an efficiency of 8.1% has been obtained at 1.2 nm s −1 .

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Gas source molecular-beam epitaxy (MBE) has been studied as a low-temperature Si and SiGe epitaxial method. Specular single-crystalline silicon films were successfully grown by the gas source Si MBE technique at a substrate temperature of about 650 °C. N-type doping was carried out using PH3 gas as a dopant and the maximum electron concentration of 2.9x1019cm−3 was obtained. Furthermore, p-type doping using B2H6 gas was carried out for the first time and the maximum hole concentration of 9.5×1017cm−3 was successfully achieved. The SiGe alloy layer was also grown by the gas source MBE technique using GeH4 as a Ge source gas. The Ge concentration of the sample could be precisely controlled by the molar fraction of Ge in supply and it was increased up to 0.30 with increasing the gas ratio of GeH4 to Si2H6.

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