Authors: L. Colalongo, M. Valdinoci, G. Forunato, L. Mariucci and M. Rudan
Affilation: University of Bologna, Italy
Pages: 447 - 452
Keywords: amorphous-silicon TFTs. impact ionization, short-channel, field-enhanced generation
Purpose of this work is to investigate the breakdown in the output characteristics of short-channel (0.2-1.o ,um) amorphous silicon (a-Si:H) thin-film transistors (TFTs). Such effect which, in the case of a-Si:H devices, has been detected for the first time by some of the authors in TFTs fabricated by electron-beam lithography (EBL), is temperature-dependent besides of being field enhanced. Because of the concurrency of severai fieldenhanced phenomena, it was necessary to supplement the investigation with numerical simulation. Thanks to the latter it was possible to rule out Poole-Frenkel, trapassisted tunneling. and band-to-band tunneling generation mechanisms, as well as the occurrence of punchthrough, which is expected at much higher source-drain `-oltages than those at which the breakdown is observed. On the other hand, avalanche generation near the drain n -intrinsic junction cannot be ruled out, and is in fact amenable to explain the current increase at large drain voltages.