Plasmonic noise in Si and InGaAs semiconductor nanolayers

Abstract

By Monte Carlo simulations we investigate the spectrum of voltage fluctuations of Si layers of variable thickness W in the range 2÷100 nm and variable length L in the range 10÷1000 nm embedded in an external dielectric medium. Calculations are performed at T 300 K for different doping levels and in the presence of an external bias of increasing strength. For W ≥ 100 nm and carrier densities of 5 × 1017 and 5 × 1018 cm-3 the peaks agree with the value of the three dimensional (3D) plasma frequency. For W ≤ 10 nm the results exhibit a plasma frequency that depends on L, thus implying that the oscillation mode is dispersive. The corresponding frequency covers a wide range of values 0.2÷10 THz and is in agreement with the values predicted by existing an alytical models. At sufficiently high bias the 2D plasma peak is washed out and we observe the onset of a peak in the sub THz region which, by analogy with the results obtained in n-InGaAs layers, is associated with transit time instabilities induced by current saturation conditions. © 2009 IOP Publishing Ltd.