A note on the assumption of quasiequilibrium in semiconductor junction devices

Abstract

The usual junction relations connecting the number densities of minority and majority carriers across the junction or depletion layer of a p-n junction are only applicable to conditions pertaining to low-level injection. Although this fact has been suspected to be true for a long time, the general consensus has been that only exact numerical calculations will reveal at which injection level the simple junction relations become incorrect. Here we wish to point out that simple algebraic manipulations of the quasiequilibrium equations valid at very low injection levels suffice to show at what injection level the quasiequilibrium theory becomes untenable under a given circumstance. Thus, a new and simple method is provided to ascertain if an extensive numerical calculation is warranted in order to obtain meaningful device characteristics.