Date of Award

Spring 2010

Document Type

Thesis - Open Access

Degree Name

Master of Science in Engineering Physics

Department

Physical Sciences

Committee Chair

Dr. Bereket H. Berhane

Committee Member

Dr. Gulamabas Sivjee

Committee Member

Dr. John Mathis

Abstract

In recent years quantum dots (QD) have attracted increasing interest because of their wide variety of revolutionary applications. Such applications include high speed optical communication lasers, infrared photodetectors, and single photon emitters. One promising immediate application is QD solar cells. Proper analysis of the optical absorption characteristics in these solar cells requires a rigorous modeling of the electronic structure and optical properties of semiconductor heterostructures. Our emphasis will be on type III-V semiconductors. Such structures, have a great potential for increasing efficiencies, but they also possess highly degenerate and complex valence band structures. Therefore, we seek to develop a model of spherical QD band structure for type III-V Semiconductor materials, and with such results we obtain the absorption properties of the simulated QDs. We assume stress and strain effects are negligible. We also assume the conduction and spin-orbit bands are treated as distant. We utilize the spherically symmetric, single and multiple band effective mass equations along with previously developed analytical methods to simplify the problem, then we obtain the eigenfunctions and eigenenergies of the QD, and use them to model optical transitions. We assume a quasi-equilibrium Fermi-Dirac distribution for electrons and holes and obtain the microscopic transition rates and absorption coefficients. Furthermore, we implement this in Matlab with a robust graphical user interface which allows for arbitrary configurations of materials and QD sizes. With this tool, the eigenenergies, eigenfunctions, and absorption coefficients may be calculated.

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