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.