4,358 research outputs found
Quasi-ballistic, nonequilibrium electron distribution in inhomogeneous semiconductor structures
We report on a study of quasi-ballistic transport in deep submicron,
inhomogeneous semiconductor structures, focusing on the analysis of signatures
found in the full nonequilibrium electron distribution. We perform
self-consistent numerical calculations of the Poisson-Boltzmann equations for a
model n(+)-n(-)-n(+) GaAs structure and realistic, energy-dependent scattering.
We show that, in general, the electron distribution displays significant,
temperature dependent broadening and pronounced structure in the high-velocity
tail of the distribution. The observed characteristics have a strong spatial
dependence, related to the energy-dependence of the scattering, and the large
inhomogeneous electric field variations in these systems. We show that in this
quasi-ballistic regime, the high-velocity tail structure is due to pure
ballistic transport, whereas the strong broadening is due to electron
scattering within the channel, and at the source(drain) interfaces.Comment: 4 pages, 2 figure
Study of an Oscillator with Two Degrees of Freedom by a Differential Analyser
Equations giving the stable amplitudes of oscillation and the conditions of stability of nil the possible modes of oscillation of an oscillator with two degrees of freedom and stabilised by a non-linearity which can be described by a third degree polynomial are given, The use of a differential analyser for the verification of these equations is illustrated. Also a method of graphically representing the transient oscillations on the analyser is described
On the Application of an Electronic Differential Analyser for Finding the Roots of a Polynomial
Electron transport in sub-micron GaAs channels at 300 K
Transient velocity-field characteristics have been computed for GaAs channels having lengths of 0.1, 0.2, 0.5, 1, and 20 µm for electric fields between 1 and 50 kV/cm at 300 K. The results are compared with earlier calculations and the significant features of the computed results are discussed. It is found that the electron motion for all channel lengths and for all fields is significantly affected by collisions. The threshold field for negative differential mobility increases, and the magnitude of the differential mobility decreases with decrease in the length of the sample. The maximum steady-state velocity increases with decrease in the length and may be as high as 5.4×107 cm/s for 0.1 µm samples
Position dependence of average electron velocity in a submicrometer GaAs channel
The Monte Carlo method has been applied to obtain the average electron velocity at different positions of a submicrometer GaAs channel in the presence of a position independent electric field. Velocity-distance curves are presented for channel lengths of 0.1, 0.2, and 0.5 µm and for lattice temperatures of 300 and 77 K. The curves show significant effects of collisions and boundary conditions
Auto-correlation of velocity-fluctuations and frequency-dependent diffusion constant for hot electrons
A method has been developed for determining the auto-correlation functions of the fluctuations in the transverse and the parallel components of hot carrier-velocity in a semiconductor by Monte Carlo simulation. The functions for electrons in InSb are determined by this method for applied electric fields of 50 V/cm, 75 V/cm, and 100 V/cm. With increasing value of the time interval the transverse auto-correlation function falls nearly exponentially to zero, but the parallel function falls sharply to a negative peak, then rises to positive values and finally becomes zero. The interval beyond which the auto-correlation function is zero and the correlation time are also evaluated. The correlation time is found to be approximately 1.6 times the relaxation time calculated from the chord mobility. The effect of the flight sampling time on the value of variance of the displacement, is investigated in terms of the low frequency diffusion constants, determined from the variation of the correlation functions. It is found that the diffusion constants become independent of the sampling time if it is of the order of one hundred times the relaxation time. The frequency-dependent diffusion constants are calculated from the correlation functions. The transverse diffusion constant falls monotonically with frequency for all the field strengths studied. The parallel diffusion constant has similar variation for the lower fields (50 V/cm and 75 V/cm) but it has a peak at about 44 GHz for the field of 100 V/cm
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