Evidence of carrier number fluctuation as origin of 1/f noise in polycrystalline silicon thin film transistors

Abstract

A systematic study of the noise performances of polycrystalline silicon thin film transistors is presented. The drain current spectral density of these devices shows an evident 1/ f behavior and scales, when operating in the linear regime, with the square of the mean value of the drain current. The origin of the noise can be ascribed to carrier number fluctuations related to the dynamic trapping and detrapping of the oxide traps.

Electrical Characteristic Analysis Using Low-Frequency Noise in Low-Temperature Polysilicon Thin Film Transistors

“…These are similar to most of the reported trap densities for poly-Si TFTs ranging from 3 × 10 18 to around 10 20 cm −3 eV −1 (Refs. [9][10]). …”

“…Recently, the carrier number fluctuation model with and without correlated mobility fluctuation ( nmodel) has been used to explain poly-Si TFT noise behaviors and estimate trap density. [8][9][10][11][12][13] To determine the dominant reason for the electrical degradation in LTPS TFT, this study now analyzes the LFN using the nmodel and the trap densities are extracted. To confirm the effectiveness of the LFN analysis, a quantitative analysis of the trap density at a grain boundary is performed following the methods of …”

Determination of bulk and interface density of states in polycrystalline silicon thin film transistors

“…In polysilicon TFTs, the origin of the low-frequency noise (LFN) is generally ascribed to carrier number fluctuations due to trapping and detrapping processes of free carriers in oxide traps located close to the gate oxide/polysilicon interface as in crystalline Si MOSFETs [3,4]. Recently, we have proposed a LFN technique to determine the density of the interface states and the slope of the exponential band tail states in the polysilicon active layer characterizing the degree of disorder of the material [5].…”

Current crowding and 1/f noise in polycrystalline silicon thin film transistors

“…Poly-Si TFTs exhibit large 1/f noise that is always attributed to carrier density fluctuations due to carrier trapping in oxide and/or grains boundary states. 10,11 Up to now, the noise in poly-Si TFTs has been interpreted only through the carrier number fluctuation with the correlated mobility fluctuation model proposed by Ghibaudo et al for crystalline-metal-oxide-semiconductor field effect-transistors (C-MOSFETs). 12 The model of correlated mobility fluctuations with carrier number fluctuation was criticized by Vandamme and Vandamme.…”