Energy Relaxation in Quantum Dots: Recent Developments on the Phonon Bottleneck

Abstract

The “phonon bottleneck” is a model proposed to explain the drop in the integrated emission intensity in semiconductor quantum dots and wires with decreasing lateral size L1. It is based on considerations of the energy spacing in these nanostructures which is typically less than the energy of an optical phonon thus leaving carrier relaxation to take place via electron-acoustic phonon scattering. In turn the electron-acoustic phonon interaction had been calculated to be reduced by orders of magnitude as the dimensionality of the system decreases from 2 to 0 2. Thus, electrons in upper energy levels spend times longer than the nonradiative scattering times and they recombine nonradiatevely leading to a decrease of the luminescence from quantum dots. Very few electrons relax to the bottom of the conduction band with the right set of quantum numbers to recombine with thermalised holes.