The high deposition of microcrystalline silicon thin film by very high frequency plasma enhanced chemical vapour deposition and the fabrication of solar cells

Abstract

This paper reports that the intrinsic microcrystalline silicon (μc-Si:H) films are prepared with plasma enhanced chemical vapour deposition from silane/hydrogen mixtures at 200°C with the aim to increase the deposition rate. An increase of the deposition rate to 0.88 nm/s is obtained by using a plasma excitation frequency of 75 MHz. This increase is obtained by the combination of a higher deposition pressure, an increased silane concentration, and higher discharge powers. In addition, the transient behaviour, which can decrease the film crystallinity, could be prevented by filling the background gas with H2 prior to plasma ignition, and selecting proper discharging time after silane flow injection. Material prepared under these conditions at a deposition rate of 0.78 nm/s maintains higher crystallinity and fine electronic properties. By H-plasma treatment before i-layer deposition, single junction μc-Si:H solar cells with 5.5% efficiency are fabricated.