The emitter efficiency of silicon bipolar transistors - An unperturbed band model

Heavy doping effects, as observed in the emitter regions of silicon bipolar devices, are usually modeled by considering an impurity-dependent band structure. In the present study it will be shown that phenomena such as reduced injection efficiency and apparent reduction of the energy gap will arise as a result of degeneracy and impurity deionization effects, even if the band structure is assumed unaltered by the presence of impurities. It will be shown that many features of the observed device behavior may be well described by means of a rather simple model.