Ambipolar transport noise in a semiconductor in the presence of a magnetic field

Abstract

The noise spectrum due to fluctuations in the electron-hole pair particle density in a semiconductor in the presence of a magnetic field is presented in this paper. This spectrum was obtained via the Green's function for the macroscopic differential equation which governs the behavior of the conditional average for fluctuations in the electron-hole pair particle density when ambipolar transport and generation-recombination are the important noise processes. The macroscopic differential equation is a generalization of van Roosbroeck's small-signal continuity equation to include the presence of a magnetic field. The resultant spectrum was evaluated numerically and a family of curves corresponding to different values of magnetic field strength generated. This was done for specified values of τ/τa and τ/τd, where τ is the mean volume lifetime of electron-hole pairs, τa is the characteristic ambipolar drift time, and τd is the characteristic ambipolar diffusion time. In the extreme situations when ambipolar drift is important and diffusion is negligible and vice versa, the obtained numerical results are consistent with those obtained previously by the author. For the case treated in this paper when both ambipolar drift and diffusion are equally important, the ``universal 3/2 power law'' still prevails in the high-frequency portion of the spectrum, thus indicating the dominance of ambipolar diffusion in that region of the spectrum.