NEGATIVE HOPPING MAGNETORESISTANCE NEAR THE CROSSOVER TO DIFFUSIVE TRANSPORT IN POLY-SI THIN-FILM-TRANSISTOR

Negative magnetoresistance (MR) due to orbital motion in the two-dimen sional variable-range hopping (2D-VRH) has been studied near the cross over to diffusive regime on n-channel poly-Si thin film transistors (T FTS) with varying gate voltage. Dependences of the observed negative M R on temperature and magnetic field agree, in tile particular regime o f Efros-Shklovskii VRH, with the theoretical predictions based on the quantum interference in VRH as similar to (T-3/2B2) in low magnetic fi elds and as similar to T-3/4B in moderate fields; even when the locali zation length xi is larger than the hopping length R-h (R-h greater th an or similar to 0.4 xi).