LOW-FREQUENCY NOISE OF THE LEAKAGE CURRENT IN UNDOPED LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITED POLYCRYSTALLINE SILICON THIN-FILM TRANSISTORS

The origin of the leakage current in low-pressure chemically vapor dep osited polycrystalline silicon (polysilicon) thin-film transistors is investigated by low-frequency noise measurements. The leakage current depends on the structure of the polysilicon layer. When the grain size is relatively large (about 120 nm), the noise spectra show a purr 1/f behavior caused by carrier fluctuation within the space charge region of the drain junction. For smaller grain size (about 50 nm), the obse rved 1/f(1.5) spectra are attributed to thermal noise of the bulk poly silicon him. (C) 1997 American Institute of Physics.