General transport theory of noise in pn junction-like devices—I. Three-dimensional Green's function formulation

Abstract

A general collective treatment of noise in three-dimensional junction devices of arbitrary geometry is presented, using Green's functions as in recent transport noise theories. The low-injection theory is extended to open-circuited devices. The density spectra are given in a form in which the volume part is linear in the Green's function and the covariance function, while the surface part is quadratic in the Green's function. The density covariance function for the short-circuited junction is Poissonian for low injection, except for a surface singularity. The noise input e.m.f and output current generator, as well as their cross correlation, are found directly for the hybrid transistor model and are expressed in the h′ parameters, without the usual network transformation. The exact results indicate distributed effects; in particular, the current gain in the noise expressions (α noise) is not equal to the small signal current gain α. The one-dimensional standard results are recovered in a lumped model approximation. For high injection, only the case of quasi band-band recombination (the Shockley-Read levels have equal capture probabilities for electrons and holes) is considered in this paper. The covariance function is then as for low injection but of half strength. The terminal noise depends, besides on the admittance or impedance and the current, on the emitter efficiency γ, the mobility ratio b, and the ratio of the junction admittance and the bulk admittance resulting from modulation effects. As a byproduct of this study, all pertinent network parameters are expressed in Green's functions.