טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSahar Vilan
SubjectElectrical and Optical Properties of Semiconductor Quantom
Dots
DepartmentDepartment of Physics
Supervisors Full Professor Gershoni David
Professor Emeritus Ehrenfreund Eitan


Abstract

This work presents experimental study of the electrical and optical properties of semiconductor quantum dots (QD). The work presents spectroscopy of single QD in specially designed samples where the dot's layer embedded in a PIN diode and optical microcavity. We have studied the influence of externally applied electric field on the dot and focused on the exciton's fine structure. In order to achieve a better understanding of the fine structure we have developed a polarization sensitive measurement system, and characterized the photoluminescence (PL) spectra of single QD under various electric fields. We have studied the influence of the electric field on the charging and discharging mechanisms in the dots and the internal interactions between confined electrons and holes at different fields.

We experimentally observed, for the first time, the fine structure of the doubly negatively charged exciton X-2, and explained the spectrum in detail with a theoretical model. The results are also supported by a numerical simulation of the optical transitions from this state. In addition, we also found an influence of strong electric field on the exciton's fine structure, and measured a significant enhancement of the electron-hole anisotropic exchange interaction with the application of strong electric fields. The experimentally measured fine structure of four different combinations of carriers in QD (X0, XX0, X-1 and X-2) are presented together with theoretical discussion.