Transistor having an emitter with a low impurity concentration portion and a high impurity concentration portion

摘要

A semiconductor device having a high current amplification gain which includes a low impurity concentration in the emitter region of the device, an injected minority carrier diffusion length L greater than the width of the emitter, and a high impurity concentration region of the same type as the emitter overlying at least a portion of said emitter region which provides a built-in-field where there is a drift current of minority carriers back toward the base region. The built-in field is larger than kT(qL) so that the drift current adjacent the built-in-field substantially cancels the minority carrier diffusion current injected from the base region.