Hydrogenated amorphous and polycrystalline silicon TFTs by hot-wire CVD

We studied the incorporation of hydrogenated amorphous silicon and polycrystalline silicon in thin-film transistors. These semiconductor layers are deposited with hot-wire chemical vapour deposition. The saturation mobility of the amorphous silicon transistors is 0.62 cm(2)/V s and the activation energy of the OFF-current and ON-current 0.77 eV and 0.12 eV, respectively. The polycrystalline silicon transistor shows 'amorphous' behaviour, with properties similar to the amorphous silicon transistor, except for the activation energy of the OFF-current (0.45 eV) which is only slightly less than that of bulk polycrystalline silicon. We conclude that the initial stage of the polycrystalline silicon growth is actually amorphous, which was confirmed by Raman spectroscopy. This amorphous incubation layer completely determines the ON-state transistor properties. We show that with hot-wire deposition, amorphous silicon thin-film transistors can be made under different deposition conditions. These transistors are stable upon gate bias stress, unlike conventional plasma-deposited amorphous silicon transistors. (C) 1998 Elsevier Science B.V. All rights reserved.