Joule Heating and Nonlinear Charge Transport in Bipolar Semiconductors

Joule heating of a homogeneous bipolar semiconductor leads to the appearance of nonequilibrium spatially inhomogeneous current carriers. Both energetic and concentration nonequilibrium states arise. Temperature and concentration gradients at the boundaries always have opposite signs. The concentration will become lower in heated regions, while it will become higher in less heated ones. Moreover, the spatial distributions of concentrations have one minimum in thin samples and two minimums and one maximum in thick samples. As a result, the current–voltage characteristic can take superlinear and sublinear forms.