Space charge capacitance spectroscopy in amorphous silicon Schottky diodes: theory, modeling, and experiments

abstract Article history:Received 12 August 2011Received in revised form 25 January 2012Available online 5 March 2012Keywords:Amorphous silicon;Capacitance spectroscopy;Density of states Numerical modeling of capacitance spectroscopy of hydrogenated amorphous silicon Schottky diodes is car-ried out. We test the accuracy of the determination of the density of states at the Fermi level, g(E F ), from ananalytical treatment of the temperature (T) and frequency (f) dependence of the capacitance (C). Assessmentof the position of the Fermi level and the attempt-to-escape frequency of states at E F is also addressed. It isshown that the precision and reliability of the determination of g(E F ) is strongly dependent on the positionof the Fermi level and the shape of the DOS and that the attempt-to-escape frequency is overestimated. Nu-merical calculations are then used to fit experimental capacitance data. Material parameters that provide thebest fits are found in quite good agreement with independent modulated photocurrent and constant photo-current measurements. Again, the attempt-to-escape frequency deduced from the simplified analytical treat-ment of capacitance data is found to be overestimated.© 2012 Elsevier B.V. All rights reserved.