Results and Case Studies

Abstract

The purpose of this chapter is to present a few results and case studies on the physics-based numerical simulation of noise in small-signal conditions for some selected classes of devices: resistors, pn diodes, field-effect and bipolar transistors. As a general remark, numerical noise modeling yields results which are in agreement with analytical approaches in all simple cases, but also enables us to cast light on more complex behaviors. Examples of the latter instance are the noise modeling of intrinsic or weakly doped short semiconductor samples, whose noise properties can significantly deviate from the Nyquist law already at comparatively low field, and the excess noise due to GR effects, whose frequency behavior in short samples is not strictly Lorentzian, with cutoff angular frequency simply equal to the inverse of the minority-carrier lifetime. Finally, numerical noise modeling can handle situations wherein analytical methods fail to provide a simple answer, as in bipolar devices under high-injection conditions, or in short-channel FETs.