Time-dependent carrier flow in a power transistor structure under nonisothermal conditions

A two-dimensional mathematical model is developed to predict the internal behavior of power transistors under transient operating conditions. The complete set of time-dependent equations governing the bipolar semiconductor transport of mobile carriers and heat flow within a transistor structure is solved by numerical techniques without assuming internal junctions and other conventional approximations. The set of partial differential equations which describe carrier transport and heat flow in a bipolar semiconductor device are approximated, temporally and spatially, by the finite difference technique. The computed results of the time-dependent analysis for a typical NPN power transistor under two operating conditions is presented, demonstrating the electrothermal interaction in this specific device.