The change of transport mechanism in μc-Si:H films induced by H2-diluted silane plasma

A hydrogen-diluted silane plasma ([H ₂]/[SiH ₄ ] in the range of 50–500) was used to prepare undoped microcrystalline silicon (μc-Si:H) films in plasma-enhanced chemical vapor deposition (PECVD) system. The transport properties of the samples were investigated by traveling wave (TW) method. The dark conductivity increases from (1.5±0.2)×10 ⁻² to (2.9±0.2)×10 ⁻² S/cm and then decreases to (5.9±0.2)×10 ⁻³ S/cm, furthermore the drift mobility monotonically increases from (8.9±0.5)×10 ⁻³ to (5.5±0.5)×10 ⁻¹ cm ²/V s, with increasing H ₂ dilution at room temperature. In the samples prepared under the condition that [H ₂]/[SiH ₄]=500, we found that the drift mobility decreases with increasing temperature, which is different from the thermal-activated phenomenon of drift mobility in normal μc-Si:H films. The change of transport mechanism in μc-Si:H samples induced by H ₂ -diluted silane plasma is discussed and related to the microstructure.