Ph.D Thesis


Ph.D StudentAngie Qarry
SubjectElectron-Polariton Scattering in Semiconductor Microcavities
DepartmentDepartment of Physics
Supervisor Professor Emeritus Cohen Elisha


Abstract

The spectroscopic and dynamic properties of cavity polaritons were studied in a microcavity having a  single quantum well that contains a 2DEG.

The polariton's properties are strongly dependent on the relative content of the exciton and the confined photon in the polariton wavefunction.  The degree of admixture is controlled by varying the detuning energy (d= EC -EX). For d< 0, the dispersion curve of the lower polariton branch forms a trap near k|| ~ 0, where the polariton radiative rate is higher than the relaxation rate of polaritons that occupy its higher energy states. Polaritons can transfer over this bottleneck by polariton - polariton scattering and, more effectively, by electron - polariton scattering.

The following topics were studied:

  1.  Spectroscopy of negatively charged polaritons

  2.  The polariton photoluminescence spectral lineshape, intensity and amplification dependence on the 2DEG density and exciton density. The observed non-linear dependence on both electron and exciton densities, was interpreted in terms of two competing scattering processes:
         a) Electron-polariton that leads to an efficient polariton transfer across the relaxation bottleneck in the lower polariton branch.
         b) Charged polariton-polariton scattering reduces the polariton density at the excitation point and in the k||~0 trap.

  3. The PL image size was measured.  The main observations were:
         a) The in-plane polariton migration from the photoexcitation spot.
         b) The migration range depends on the polariton branch and for
    d<0 it extends over a large in-plane distance of ~300mm.
         c) Introducing a 2DEG into the QW reduces the migration range, and enhances the intensity of the LP emission.