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Hot-electron magnetotransport and fluctuation noise in quantum wires
Abstract
This dissertation contains a detailed theoretical investigation of hot-electron magnetotransport in quasi one-dimensional semiconductor structures. Additionally, Johnson and 1/f noise have been studied using Monte Carlo simulation. The theoretical model employed in this dissertation has rigorously taken into account acoustic and optical phonon, as well as electron confinement and dispersion relation in calculating electron-phonon scattering rates in the presence of a magnetic field. Specifically, we derived confined and surface acoustic phonon normal modes by numerically solving the elasticity equation with appropriate mechanical boundary conditions. We found that acoustic phonon confinement increases electron scattering rates by several orders of magnitude and qualitatively modifies the phonon dispersion relation. The ratio of absorption to emission rates can be larger than unity in narrow intervals of energy thereby making the energy relaxation rate in these intervals negative. An external magnetic field always decreases the momentum relaxation rate even though the scattering rate may increase or decrease depending on whether the interaction is polar or non-polar. Another surprising finding is that the velocity and momentum relaxation rates (which are identical in a parabolic band in the absence of a magnetic field), are qualitatively different when a magnetic field is present (they can even have opposite signs!). The calculated scattering rates were subsequently used to solve the Boltzmann Transport Equation employing Monte Carlo technique. Statistics of velocity fluctuations were used to find the velocity autocorrelation function, the noise power spectrum and the dc component of hot carrier diffusivity. The colored noise spectra contain clear signatures of phonon quantum confinement. Oscillations show up in the velocity correlation function owing to carrier streaming and contribute to strong peaks in the noise spectral density. A magnetic field decreases the rate of temporal decay of the velocity correlation function by decreasing effective momentum relaxation rate and promotes streaming oscillations. This has an effect of transferring noise power from low to high frequency end of the spectrum. A magnetic field can thus be used to quench noise in quantum wire structures.
Subject Area
Electrical engineering|Electromagnetics
Recommended Citation
Svizhenko, Alexei, "Hot-electron magnetotransport and fluctuation noise in quantum wires" (1999). ETD collection for University of Nebraska-Lincoln. AAI9917863.
https://digitalcommons.unl.edu/dissertations/AAI9917863