Date of Award

Summer 2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Applied Physics - (Ph.D.)

Department

Federated Physics Department

First Advisor

Anthony Fiory

Second Advisor

N. M. Ravindra

Third Advisor

John Charles Hensel

Fourth Advisor

Tao Zhou

Fifth Advisor

Zhen Wu

Sixth Advisor

Martin Lepselter

Abstract

The objective of this thesis is to explore superconductivity in semiconductor superlattices of alternating hole and electron layers. The feasibility of superconductivity in semiconductor superlattices is based on a model formulated by Harshrnan and Mills. In this model, a semiconductor superlattice forms the layered electron and hole reservoirs of high transition temperature (high-Tc) superconductors.

A GaAs-A1xGa1-xAs semiconductor structure is proposed which is predicted to superconduct at Tc = 2.0 K and may be analogous to the layered electronic structure of high-Tc superconductors. Formation of an alternating sequence of electron- and hole-populated quantum wells (an electron-hole superlattice) in a modulation-doped GaAs- A1xGa1-xAs superlattice is considered. In this superlattice, the distribution of carriers forms a three-dimensional Wigner lattice where the mean spacing between carriers in the x-y plane is the same as the periodic distance between wells in the superlattice. This geometrical relationship mimics a prominent property of optimally doped high - Tc superconductors.

A Schrodinger-Poisson solver, developed by Snider, is applied to the problem of determining the appropriate semiconductor layers for creating equilibrium electron-hole superlattices in the GaAs-A1xGa1-xAs system. Formation of equilibrium electron-hole superlattices in modulation-doped GaAs-A1xGa1-xAs is studied by numerical simulations. Electron and heavy-hole states are induced by built-in electric fields in the absence of optical pumping, gate electrodes, or electrical contacts. The GaAs-A1xGa1-xAs structure and the feasibility of meeting all the criteria of the Harshman model for superconductivity is studied by self-consistent numerical simulation.

In order to test the existence of superconductivity, the physics of sensor arrays and their ability to create synthetic images of semiconductor structures, is explored. Approximations are considered and practical applications in detecting superconductivity in superlattices are evaluated.

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