Emitter efficiency and injection level in diffused structures

The differential equations governing the transport of injected carrier densities in inhomogeneous semiconductors are set up and solved for low and high injection levels. The solutions are applied to the flow of current in the base and emitter regions of transistor structures obtained by solid-state diffusion techniques. This leads to the establishment of the criteria for the onset of high-injection conditions which entail the limitation of the speed of response. The analysis indicates the optimum structural parameters for a fast-response high-current diffused transistor.