High-frequency effects of the potential minimum on noise

Abstract

A physical model of the compensation phenomenon in space-charge reduced shot noise is discussed in some detail and applied first to a planar diode of infinite spacing short-circuited to ac effects. Analysis of both the time response and frequency response shows that parameters of the potential minimum are very important to the degree of noise compensation or over-compensation, and for certain parameters the internal feedback mechanism of returning charges may cause a self oscillation without external stimuli, or in other words a building-up to saturation levels of noise phenomena in these frequency ranges. For other parameters of the minimum there appear to be very complete compensation phenomena possible, but practical parameters for this were not found in the infinite spacing case. The infinite spaced short-circuited diode gives results in exact agreement with the frequency domain analysis of the open-circuited diode as analyzed by Siegman and Watkins. Some additional approximations may be made in this analysis for qualitative explorations, particularly important being the consideration of only a single velocity class of noise perturbation. The short-circuited diode of finite spacing is analyzed in both the frequency domain and time domain, and an approximate correction to the above results found as a function of total transit angle across the diode. In particular, the factor produces appreciable decreases in the reduction factor in the vicinity of certain transit angles across the diode, and as the Tien dips occur in these general ranges, the finite diode spacing is believed to be a strong candidate for explanation of these dips.