Plasmonic Noise in Nanometric Semiconductor Layers

By means of numerical simulations we investigate voltage and current fluctuation spectra of an n-type In0.53Ga0.47As layer of thickness W and submicron length L at T = 300 K. In agreement with theoretical expectations, for a plasma time longer than the dielectric relaxation time, the spectral density of the voltage fluctuations is found to peak at the plasma frequency before cut-off. For W = 100 nm and carrier concentrations of 1016–1018 cm−3 the results of simulations reproduce the standard 3D expression for the plasma frequency. For W≤10 nm the results exhibit a plasma frequency (plasmonic noise) that depends on L, thus implying that the oscillation mode is dispersive. The corresponding frequency values are in good qualitative agreement with the 2D expression for the plasma frequency obtained for a collisionless analytical model using the in-plane approximation for the electric field. A set of novel results not predicted by the analytical model are particularized and discussed.