CHARACTERIZATION AND MODELING OF THE POWER INSULATED GATE BIPOLAR TRANSISTOR.

摘要

The power Insulated Gate Bipolar Transistor (IGBT) is a new switching device designed to overcome the high on-state loss of the power MOSFET. The IGBT behaves as a bipolar transistor which is supplied base current by a MOSFET. The bipolar transistor of the IGBT has a wide base with the base contact at the collector edge of the base and is operated with its base in high-level injection. Because of this, the traditional bipolar transistor models are not adequate for the IGBT and the new model developed in this dissertation must be used. The new model is developed using ambipolar transport and does not assume the quasi-static condition for the transient analysis.; The new IGBT model is used to describe measurements for extracting the essential physical device parameters of the model. With these extracted parameters, the new IGBT model consistently describes the measured electrical characteristics of IGBTs with different base lifetimes. The important electrical characteristics of the IGBT are the on-state I-V characteristics, the steady-state saturation current, and the switching transient current and voltage waveforms. The transient waveforms are examined in detail for constant anode voltage switching, clamped inductive load switching, and series resistor, inductor load switching.; The disadvantage of the IGBT is its slow turn-off speed relative to that of the power MOSFET. The two methods which have been proposed to reduce the turn-off time of the IGBT are base lifetime reduction and buffer layer inclusion. Both methods have the disadvantage, though, of also increasing the on-state voltage. The buffer layer is a high-doped portion of the bipolar transistor base at the base-emitter junction. The new IGBT model discussed above is extended to include the buffer layer. Using the extended model, it is shown that the buffer layer IGBT can be made to have a faster switching time for a given on-state voltage than that of the nonbuffer layer (lifetime reduction) IGBT.; In summary, a new model is developed for the IGBT. It is shown that the new model must be used to accurately describe the steady-state and transient characteristics of the IGBT. The model is used to compare the effects of lifetime reduction and buffer layer inclusion. The results of the comparison show that a better on-state voltage, switching speed trade-off is obtained using the buffer layer than is obtained using lifetime reduction.