Boundary condition for evaluating minority base charge in bipolar transistors

In the letter, a formula for the minority density at the boundary between the neutral base region and the collector transition region of bipolar transistors is derived. The formula is applied to the `regional? evaluation of the electron distribution in the base of a 1-dimensional n?p?n transistor. The results obtained in this way are shown to be in good agreement with those of numerical solutions of the system of differential equations formed by Poisson's law and the transport and continuity equations.