Subject of the dissertation is the investigation of physical modeling bipolar power semiconductor devices (silicon) in the temperature range between 400K and 100K. The main task are the investigation of the validity of adequate transport equations and the elaboration of fundamentals for developing compact network models. The results are also covering modeling fundamentals in general, e.g. device simulations. The static and transient pecularities of bipolar power semiconductors are predominated by the properties of the low doped drift layer. Thus particular effects of charge carrier interactions have to be correctly taken into account. Since there are significant uncertainties of describing carrier mobilities when the influence of electron-hole-scattering is becoming predominant the presented work may contribute to clear up the situation. For doing this the most proper devices are structures of power diodes. Thus other complicating effects as occuring in devices like IGBTs or GTOs have to be not taken into account. A consistent set of modeling equations is presented. The descriptions of basic doping and temperature effecs are discussed. Significant importance is attached to the formulation of carrier mobilities with particular respect to electron-hole-scattering. Properties of the sophisticated mobility description by Mnatsakanov are discussed and compared with standard formulations. In order to take the specific pecularities of the Mnatsakanov mobility theory into account, a new continuity equation is derived and characterized. A complete and temperature dependent power diode model is developed. The validation was done not only by standard electrical measurements, but additionally by infrared (IR) absorption measurements for probing the device internal spatial and temperature dependent carrier concentrations. For that a temperature controled optical cryostat was designed. The experimental techniques and experiences are described. For analyzing these firstly performed temperature dependent IR absorption measurements, the temperature dependent free carrier absorption coefficient for the wavelength of 1.32e-6m was calibrated between 150K and 400K. The experimental results of the static electrical diode characteristics and device internal carrier distribitions are compared with according simulated results. By using a standard diode model in comparison to the here presented model it is shown that the obtained simulated results are not consistent, when standard formulations of carrier mobilities and of the continuity equation are used. At conditions with increasing predominant significance of carrier-carrier interactions for carrier mobility, i.e. at temperatures below 250K, voltage drops as well as carrier concentration are calculated definitely too small. This problem can be not solved by simply adapting equation parameters. The better the simulated voltage results coincide with the measurements the more the discrepancies of the carrier concentrations are increasing, respectively vice versa, too. However good results are obtained by applying the here presented diode model. All calculated voltage drops excelently coincide with measurements, as well as the simulated spatial carrier concentrations between 400K and 200K. For lower temperatures the bending of the carrier distribution is overestimated which is due to the used carrier lifetime model. Nevertheless the calculated quantities are within a sufficiently acceptable common range with the measured carrier concentrations at 100K. Finally consequences of the found results for modeling power devices are drawn and discussed in general.
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Subject of the dissertation is the investigation of physical modeling bipolar power semiconductor devices (silicon) in the temperature range between 400K and 100K. The main task are the investigation of the validity of adequate transport equations and the elaboration of fundamentals for developing compact network models. The results are also covering modeling fundamentals in general, e.g. device simulations. The static and transient pecularities of bipolar power semiconductors are predominated b...
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