Monte Carlo analysis of the behavior and spatial origin of electronic noise in GaAs MESFET´s

We present a Monte Carlo (MC) analysis of electronic noise associated with velocity and field fluctuations in GaAs MESFET´s. To this end, an accurate estimator of the instantaneous currents at the terminals is used, which improves the precision of the method. Both the current and voltage fluctuations at the different terminals of the device are investigated, thus allowing for the spatial localization of the noise sources. Three different MESFET geometries are analyzed. The results so found compare well with experimental results and confirm the general trend provided by existing phenomenological noise modeling. As a general result, the noise in the drain current is found to increase with the level of the current and remain constant with frequency at least up to 100 GHz. In the case of the gate current, the noise is null at low frequency and then increases quadratically. Under saturation conditions, the source of the drain-voltage fluctuations is localized at the drain end of the n channel, and even penetrates the drain n⁺ region due to the presence of hot carriers in the upper valleys