Contact Effects in High Mobility Microcrystalline Silicon Thin-Film Transistors

Abstract

AbstractMicrocrystalline silicon (mc-Si:H) has recently been proven to be a promising material for thin-film transistors (TFTs). We present mc-Si:H TFTs fabricated by plasma-enhanced chemical vapor deposition at temperatures below 200°C in a condition similar to the fabrication of amorphous silicon TFTs. The mc-Si:H TFTs exhibit device mobilities exceeding 30 cm2/Vs and threshold voltages in the range of 2.5V. Such high mobilities are observed for long channel devices (50-200 mm). For short channel device (2 mm), the mobility reduces to 7 cm2/Vs. Furthermore the threshold voltage of the TFTs decreases with decreasing channel length. A simple model is developed, which explains the observed reduction of the device mobility and threshold voltage with decreasing channel length by the influence of drain and source contacts.