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The classical impedance field method is one of the most powerful techniques to calculate electronic noise in semiconductor structures. This method fails when applied to deep submicron devices due to the presence of spatial correlations between noise sources. To overcome this drawback, a new technique (generalised impedance field) has been developed in the frame of a hydrodynamic simulator. Analogously to the classical method, the calculation of electronic noise requires the knowledge of two quantities: the local noise sources and the generalised impedance fields. Instead of using a hydrodynamic approach to obtain the generalised impedance fields and a Monte Carlo simulation for the noise sources, we have used a microscopic simulator (the Scattered Packet Method) to compute both quantities.

We survey recent results on electronic noise in nanostructured devices. Three kinds of excess noise referring to hot-carriers in submicron n+nn+ diodes, shot noise in mesoscopic structures, resistance fluctuations in thin film conductors, are considered. The influence of down-sizing on fluctuations is illustrated in each case.

High electron-mobility transistors can be used as efficient detectors of an incident THz radiation on its metallic electrodes. This detection can become strongly resonant if the frequency of the THz radiation coincides with plasma eigenfrequencies of the transistor channel. By using a hydrodynamic model we investigate in parallel the transistor intrinsic high-frequency current noise spectrum and its harmonic and average current responses to a voltage perturbation at the electrodes. In both cases we discuss the appearance of resonances associated with the excitation of 2D and 3D plasma modes and, to get an additional physical insight into the properties of the different parts of the transistor, we compute also the local noise spectra originated by electron velocity perturbations distributed in the channel. We demonstrate that the main resonances in the drain current noise spectrum are the same as those observed in the current response to an external THz excitation thus confirming the strong link existing between these two quantities.

In this contribution we propose an analytical approach for the calculation of the high-frequency noise spectrum of frequency multipliers based on n+n-metal Schottky-barrier diodes and n+n - barrier - nn+ Heterostructure-barrier varactors. The model includes a diodes operating in series with a parallel resonant circuit to extract the harmonics generated in the terahertz frequency region.

The authors present a novel hydrodynamic approach to the study of DC and AC hot-carrier transport in semiconductors. To this end use is made of a total-energy scheme which incorporates simultaneously the kinetic and potential energy associated with different conduction band minima. Furthermore, convective and diffusive contributions are considered by including the variance of velocity-velocity and velocity-energy fluctuations. Together with static characteristics, a small-signal analysis under spatially homogeneous conditions of the most important response functions of the electron system (e.g. differential mobility, diffusivity, velocity-noise spectrum, etc) is developed consistently. The validation of the present approach is supported by an excellent comparison with Monte Carlo results carried out for the case of n-Si at 300 K.

Measurements of terahertz resonant emission due to the excitation of plasma waves by an optical beating inside AlGaAs/InGaAs/InP high electron mobility transistors are reported at 300 K and 200 K.

In this paper we propose an analytical model for the calculation of the spectral density of current fluctuations in Heterostructure-barrier varactors . The structures of the calculated spectra are analyzed in terms of physical processes useful to optimize the device parameters for the extraction of the high-order harmonics.

We present a theoretical analysis of the thermal conductivity of charge carriers in semiconductors under nonequilibrium conditions due to an applied electric field. The theory is based on a correlation-function formalism which directly relates this kinetic coefficient to four spectral densities involving carrier velocity and energy flux fluctuations. Monte Carlo calculations performed for the cases of p-Si and n-GaAs give an evidence of a strong dependence of the thermal conductivity on increasing electric fields.

We investigate the possibility to suppress the diffusion noise in semiconductor bulk materials by adding to the constant electric field a fluctuating contribution characterized by a gaussian distribution and a characteristic time. The general theory is applied to the specific cases of Si and GaAs and investigated by Monte Carlo simulations. Numerical results confirm the possibility to suppress the intrinsic noise and the best conditions to realize this effect are analyzed in detail.

This paper overviews and implements the transfer-field method applied to the calculation of electronic noise in small semiconductor structures. Two basic schemes are used and developed in detail. The former considers velocity fluctuations and the latter acceleration fluctuations as microcopic noise sources. We show that the latter scheme has several advantages with respect to the former one. Indeed, starting from Markovian noise sources, the latter scheme separates the time and spatial evolution of the local noise sources. In this way, the dual representation of the noise spectral density in terms of impedance and admittance fields is recovered. A remarkable achievement is that from the knowledge of the bulk Langevin sources at a hydrodynamic level it is possible to calculate the noise spectra of non-homogeneous structures even for nanometric devices. The method is validated by comparing the results of the present scheme with those obtained from self-consistent Monte Carlo approaches for different structures of interest.

One of the most suitable techniques to compute noise in electronic devices is the standard impedance field method, a deterministic approach able to provide analytical and numerical solutions for the noise spectra of electronic devices at a hydrodynamic (HD) level. The starting point of our investigation consists in showing that this method is not appropriate for the calculation of noise spectra in deep submicron devices where spatial correlations between noise sources are of relevant importance. To overcome the difficulties which are intrinsic to the standard impedance field method we have developed a new scheme based on Langevin forces and generalized transfer fields.

We present a theoretical investigation on the electrical behavior of submicrometer n+nn+ diode microwave generators. To this end we adopt a mixed scheme which uses space‐homogeneous and stationary Monte Carlo simulations to provide the input parameters for a hydrodynamic analysis of the diode performances. Comparison between GaAs and InP made devices working at 400 K give similar results by predicting generation frequencies up to 700 GHz for an active region length of 0.2 μm.