A novel approach of immittance-spectra analysis and how it resolves a decade-old deviation of the Frenkel-Poole model

Abstract

As already indicated above, this work focuses primarily on the development of a novel method to analyse experimentally obtained immittance spectra by using process-speci c physical models dependent on external parameters. Ultimately, this allows the extraction of process-speci c parameters which are inherently linked to a physical meaning (e. g. an acceptor concentration or a barrier height, instead of a resistance or a capacitance) and can, hence, be better compared between experiments. Furthermore, the introduction of models with dependence on external parameters eliminates circuit ambiguity which, as can be seen in Figure 1.1, also improves the comparability between di ferent experiments. Moreover, the regions of importance for the respective processes are automatically weight by the parameter-dependence of the models. Additionally, external-parameter dependence enhances the association of circuit components with distinct pieces of the system under investigation and reduces the absorption of deviations, e. g. by an incomplete model on one piece, into the t parameters of another piece. Finally, if the same underlying physical properties are present in di ferent models for the same piece they may be shared and, consequently, tted jointly, even between capacitive and resistive properties.The application of this novel approach on samples with ta-C lms on p-type silicon substrates, with di ferent doping concentration, is only an example. However, as explained below, a carefully chosen one.The analysis of depletion layers in silicon, usually in form of capacitance-voltage measurements, is probably one of the most common applications of immittance spectroscopy in semiconductor physics. In comparison to many other systems investigated by immittance spectroscopy, which often rely on empiric models, depletion layers are relatively well-investigated and -understood phenomena which have theory-based models [138][176, pp. 245-297]. The latter is not only true for the capacitance of a depletion layer, but also for its resistance-voltage characteristic, i. e. its static current-voltage relation [176, pp. , 245-286]. As already explained, the novel approach in this work is based on introducing physical models dependent on external parameters. In the case of the depletion layer, both resistive and capacitive properties are dependent on the external parameter voltage and both models are based on microscopic assumptions (which is what is meant in this work by physical model dependent on external parameters). Voltage-dependent immittance spectra, as those obtained in this work, not only contain the capacitancevoltage information, but also the full resistance-voltage characteristic. Furthermore, the higher number of frequencies in the approach introduced in this work as compared to conventional capacitance-voltage analysis (often only one high-and one low-frequency measurement are performed [138, pp. 321-333, 388-389]) allows distinguishing and potentially identifying di ferent serial parts in the system. This allows identifying...