Introduction to special issue on noise modeling

Electronic noise is a limiting factor in many applications of semiconductor devices and integrated circuits. The fluctuations of electronic signals around their average (or cyclostationary) value can make impossible the recognition of the signal being processed or detected, which remains hidden by the noise generated by the device or the circuit. This can be particularly critical when working with low-power signals, like in many applications related to communications or remote sensing. Fluctuations reflect the presence of the many processes taking place at a microscopic level and having an influence on macroscopic quantities like voltages or currents. The exact knowledge of such microscopic processes at the origin of fluctuations, and how they are transferred to the terminals of the devices, and eventually amplified or frequency-shifted in a given circuit, is essential for the control of the noise level in advanced electronic systems. Thus, efforts at material, device and circuit levels are necessary. Different types of noise sources must be considered to cover the full scenario when going from low to high frequency: the thermal noise inherent to the materials, transformed into hot-carrier noise when operating under far from equilibrium conditions; the ubiquitous 1/f noise, described by theories based on mobility and/or number fluctuations; generation-recombination (GR) noise originated by carrier trapping, with cutoff frequencies related to the carrier lifetime; shot noise associated to carrier granularity; etc. Additionally, correlation between noise sources must be taken into account. Processes of noise upconversion originated by the nonlinear response of devices and circuits must be also