We present a novel hydrodynam'c approach to tne stuoy of oc and AC hot-carrier transpon in sem:conducrors. To In's end Lse is made of a total-energy scheme which incorporates simullaneoJsly tne kinetic and potential energy associated with d:fferent conouction band min ma. Funhermore, wnvect;ve ano oiffusive Contr'bJtions are wns:dered by incluoing the variance of velocityveloc'ty an0 velocity-energy flJctJations. Together w'th'sta1:c cnaracteristics, a sma I-signal analysis Jnder spatially homogeneox mnoitions of the most .mportant response fJnctions of the electron sysrem (e.g. o.Herentia mooi ty, d'ffusiv'ty, ve ocity-noise spectrum etc) is oeveloped consistent y. Tne valioat'on of the present approacn is sLpponecl oy an excel ent comparison w:th Monte Carlo results carrieo out for the case of n S i at 300 K

We present an analytical modeling of the noise temperature associated with velocity fluctuations obtained in the framework of the linear-response theory around a steady state. The expressions are rigorously related to an eigenvalue expansion of the response matrix and are applicable to ohmic as well as to nonohmic ͑hot-carrier͒ conditions. Theory requires as input parameters the reciprocal carrier effective mass, the drift velocity, the carrier energy, the variance of velocity fluctuations, and the covariance of velocity-energy fluctuations as functions of the electric field in stationary and homogeneous conditions. The analytical results obtained for the case of holes in Si and electrons in GaAs at Tϭ300 K are validated by comparison with experiments.

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.

We present analytical expressions for the differential-mobility spectra which are obtained from a linear analysis of the balance equations under stationary and homogeneous conditions. The expressions are rigorously related to an eigenvalue expansion of the response matrix and are applicable to ohmic as well as to non-ohmic conditions. The coefficients appearing in the formula can be calculated from the knowledge of three parameters as functions of the electric field, namely, the reciprocal effective mass, the drift velocity, and the average energy of the carriers. The theory is applied to the case of holes in Si at T= 300 K and validated by comparison with the results obtained by a direct numerical resolution of the perturbed Boltzmann equation. 0 1995 American Institute of Ph.ysics.

We analyze electronic noise in field-effect transistors associated with plasma waves in the terahertz frequency domain by using a numerical approach based on the coupled hydrodynamic and Poisson equations. The current and voltage noise spectra, calculated by means of the transfer impedance method, exhibit a series of peaks associated with two- and three-dimensional plasma resonances. The two-dimensional plasma peaks have been found to depend on the channel length including gated and ungated regions. Under asymmetric boundary conditions, electrical instabilities characterized by terahertz oscillations of the drain voltage and gate current can be reached at sufficiently high values of the total drain current. A resonant enhancement of the plasma peaks in the noise spectra has been found to be a precursor of the instability onset. Through a spatial analysis of the local contributions we have shown that the main contribution to the total noise at frequencies near the plasma resonance comes from the ungated n-region placed between the source and the gate contacts.