Field-effect analysis for the determination of gap-state density and Fermi-level temperature dependence in polycrystalline silicon

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Abstract
The field-effect conductance has been used in two distinct ways to determine the gap-state density in polycrystalline silicon. The relationship between the surface potential and the gate voltage, which determines the gap-state density, has been deduced according to the incremental method, already proposed by Suzuki et al., and a new method. The new method is based on the temperature dependence of the derivative of the field-effect conductance with respect to the gate voltage. The results from the two methods are in good agreement and show a rapidly increasing gap-state density in the upper half of the gap. The temperature analysis of the field-effect conductance indicates that the position of the Fermi level is temperature dependent. The contribution to this dependence from the statistical shift has been determined.