Modelling bulk and surface recombination in the sidewall space-charge layer of an emitter-base junction

The sidewall space-charge region of an emitter-base junction is of importance in the determination of low current gain fall-off where both bulk and surface recombination dominate. The paper discusses the behaviour of this region using results from two different numerical analyses. A previously defined modelling parameter to represent surface recombination effects is computed from physical data and the contribution to recombination currents from three distinct regions (surface, bulk sidewall and bulk vertical) is compared. Experimental determination of the parameter is discussed and values given for a typical process.