A comprehensive analytical on-current model for polycrystalline silicon thin film transistors based on effective channel mobility

Abstract

A comprehensive analytical ON-state drain current model for poly-Si thin film transistors (TFTs) is developed to accurately fit both transfer and output characteristics of either low or high temperature processed poly-Si TFTs in both n- and p-types, with the same unified analytical form. The model is physical explicitly based and mathematically accurate, with no artificial factors introduced. To accomplish this, (1) the most appropriate model precisely describing the gate voltage dependent mobility degradation effect in poly-Si TFTs is determined from three previously employed models; (2) grain boundary barrier controlled carrier conduction model is adequately incorporated; and (3) a mathematically accurate analytical form for drain current is derived based on gradual channel approximation by introducing a new fitting parameter to describe the effective average channel mobility. Channel length modulation effect is introduced in modeling output characteristic. Applicability and accuracy of the model are demonstrated by fitting both n- and p-types poly-Si TFTs fabricated from very different processes.