Two-dimensional nonisothermal carrier flow in a transistor structure under reactive circuit conditions

The current density and temperature distribution in a bipolar power transistor operating in the switching mode under transient conditions is computed as a function of circuit environment. The method of computation is to solve numerically the electrical carrier flow as well as Poisson and the heat flow equations in a two-dimensional model of an n⁺-p-n-n^-transistor structure, as a function of time. Of particular interest is the behavior of the local current and temperature distribution achieved in the transistor during turn-off in a circuit with a large inductance. The length of time that the transistor remains in the high current, high voltage mode during the turn-off transient determines the extent of current crowding and local heating in the device.