Electron localization in band-tail transport of high-mobility poly-Si TFTs

Abstract The results of low-temperature transport properties on high-mobility poly-Si thin film transistors (TFTs) have been examined by measurement of the resistance as a function of temperature, magnetoresistance (MR) and Hall effect. It has been shown that the transition between the two-dimensional (2D) weak and strong localization (WL and SL) occurs around the sheet resistance R = π h /e 2 (⋍ 13 kΩ), where ( 1 2 )k F l ∼ 1 , in the band-tail states, caused by potential fluctuations in the inversion layer of TFTs. In the barely SL regime, R at low temperatures is found to obey the Efros-Shklovskii variable-range hopping (VRH) law in the presence of the Coulomb gap in the density of states. In both regimes of WL and SL, a negative MR has been observed and interpreted by the quantum interference effect in each regime.