HYDROGENATED AMORPHOUS AND POLYCRYSTALLINE SILICON TFTS BY HOT-WIRE CVD

We studied the incorporation of hydrogenated amorphous silicon and pol ycrystalline silicon in thin-film transistors. These semiconductor lay ers are deposited with hot-wire chemical vapour deposition. The satura tion mobility of the amorphous silicon transistors is 0.62 cm(2)/V s a nd 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 sil icon. We conclude that the initial stage of the polycrystalline silico n growth is actually amorphous, which was confirmed by Raman spectrosc opy. This amorphous incubation layer completely determines the ON-stat e transistor properties. We show that with hot-wire deposition, amorph ous silicon thin-film transistors can be made under different depositi on conditions. These transistors are stable upon gate bias stress, unl ike conventional plasma-deposited amorphous silicon transistors. (C) 1 998 Elsevier Science B.V. All rights reserved.