Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 50: ZnO: Tansport
HL 50.4: Talk
Thursday, February 28, 2008, 14:45–15:00, ER 164
Modelling of the frequency and temperature dependence of ZnO Schottky diode capacitance — •Martin Ellguth1, Matthias Schmidt2, Alexander Lajn1, Holger von Wenckstern1, Rainer Pickenhain1, and Marius Grundmann1 — 1Universität Leipzig, Leipzig, Germany — 2Forschungszentrum Dresden–Rossendorf e.V., Dresden, Germany
Understanding conduction in semiconductors requires knowledge about incorporated electrically active defects. Commonly, capacitance–spectroscopical methods like capacitance–voltage, deep level transient– and thermal admittance spectroscopy (TAS) are used to characterize these defects. We analyze such measurements by modelling the current–free Schottky diode capacitance. We solve numerically Poisson’s equation as well as the donor occupancy time–evolution.
Our model gives exact solutions for the temperature, voltage and probing frequency dependence of the capacitance. In contradiction to classical TAS analysis, our simulation models entire capacitance–temperature/frequency spectra instead of obtaining the defect parameters (energetical depth, concentration, and electron capture cross section) only from the turning points in measured spectra. Additionally, line shape analysis allows the determination of the concentrations of two energetically close–lying levels which cannot be obtained from classical TAS analysis. We applied our simulations on TAS data obtained from ZnO single crystals and thin films and were able to improve the accuracy of the values for the electron capture cross section and to determine the respective concentrations for each defect.