Ambipolar thin-film transistors fabricated by PECVD nanocrystalline Silicon

We report on directly deposited plasma-enhanced chemical vapor deposition (PECVD) nanocrystalline silicon (nc-Si:H) ambipolar thin-film transistors (TFTs) fabricated at 260 degrees C. The ambipolar operation is achieved adopting Cr metal contacts with high-quality nc-Si:H channel layer, which creates highly conductive Cr silicided drain/source contacts, reducing both electron and hole injection barriers. The n-channel nc-Si:H TFTs show a field-effect electron mobility (mu cFE) of 150 cm(2)/Vs, threshold voltage (V-T) similar to 2 V, subthreshold slope (S) similar to 0.3 V/dec, and ON/OFF current ratio of more than 107, while the p-channel nc-Si:H TFTs show a field-effect hole mobility (mu hFE) of 26 cm(2)/Vs, V-T similar to -3.8 V, S similar to 0.25 V/dec, and ON/OFF current ratio of more than 10(6). Complementary metal-oxide-semiconductor (CMOS) logic integrated with two ambipolar nc-Si:H TFTs shows reasonable transfer characteristics. The results presented here demonstrate that low-temperature nc-Si:H TFT technology is feasible for total integration of active-matrix TFT backplanes.