Ambipolar charge transport in microcrystalline silicon thin-film transistors

Hydrogenated microcrystalline silicon (μc-Si:H) is a promising candidate for thin-film transistors (TFTs) in large-area electronics due to high electron and hole charge carrier mobilities. We report on ambipolar TFTs based on μc-Si:H prepared by plasma-enhanced chemical vapor deposition at temperatures compatible with flexible substrates. Electrons and holes are directly injected into the μc-Si:H channel via chromium drain and source contacts. The TFTs exhibit electron and hole charge carrier mobilities of 30–50 cm2/V s and 10–15 cm2/V s, respectively. In this work, the electrical characteristics of the ambipolar μc-Si:H TFTs are described by a simple analytical model that takes the ambipolar charge transport into account. The analytical expressions are used to model the transfer curves, the potential and the net surface charge along the channel of the TFTs. The electrical model provides insights into the electronic transport of ambipolar μc-Si:H TFTs.