A Static Characteristics Research Based On Surface Potential For A-Si:H Thin-Film Transistors

Amorphous silicon thin film transistor (a-si:H TFT) as a switch components as well asdriving circuit is widely used in display field, with broad application prospect. The goal ofthis paper is analyzed the current characteristics and temperature characteristics of a-si:H TFTdevices,then based on the surface potential model, proposed the unified I-V model of thea-si:H TFT.The located state density distribution of the Amorphous silicon thin film play animportant influence to the a-si: H TFT electrical characteristics. The continuous, doubleexponential distribution model in the energy band is a valid description to the a-si:H TFTdensity distribution. The calculation of the surface potential, current-voltage unified model,temperature effect and the analysis of double gate a-si: H TFT all are getting based on thedouble exponential distribution descriptionthe in considering both deep and tail state.Based on the surface potential method provides the ideas based on physical modeling.This paper taking into account both the deep state and tail state in Poisson’s equation,established the implicit equation about the surface potential, the implied equation describesthe surface potential with the gate voltage function relations. Combined with the concept ofeffective temperature, this paper established a-si: H TFT unified current and voltage model,the model can describe all work area of a-si: H TFT includes subthreshold region, linear areaand saturated zone but with no division. This model successfully explain how the located stateinfluenced the regional characteristics, especially in the saturated area. At the same time, thisarticle analyzed the effective temperature with the change of the surface potential,and knewthat the effective temperature comprehensive embodies the deep state, with tail states, plusfree electrons with the change of the gate voltage, and does not need to separate to discusswith tail state and deep state. In the different voltage consider different concentrations ofleading carriers, given simple method about the amount of free charge carriers, and compareto the experimental data proves this method can correctly to get the carriers concentrationwith the change of the surface potential relationship.In practical applications, a-Si TFT electrical properties are influenced by temperature,based on the surface potential, this paper analyzed the temperature effect, and get the a-SiTFT electrical properties with the change of the temperature relations.According to the opening of the rate of that request, and based one electric properties ofthe single gate a-si:H TFT, set up the unified current-voltage equation of the double gate a-SiTFT,and analyzed the relationship of surface potential chang with the gate voltage between the front and back channel.The results show that, with the charge coupling effect betweenthe front and back channel, the properties of the double gate a-Si TFT is different from thesingle gate a-Si TFT.