Quantum well to quantum dot phonon-assisted tunneling

Abstract

There has been great interests on semiconductor quantum dot (QD) due to its novel physical properties and potential applications such as semiconductor lasers with high gain and narrow linewidth. The collection of carriers by the QDs is a critical issue for efficient gain of QD lasers. A tunneling injection quantum-dot laser has been researched recently. Direct, photon-, phonon-, and Auger-assisted tunneling are all possible mechanisms for carrier transfer from QW to QD. In this talk, we present a theoretical model for the phonon-assisted tunneling from a quantum well (QW) state to the QD ground state in the conduction band. We assume a quantum-disk model and use its analytical wave functions to calculate the tunneling rate based on Fermi's Golden rule. The single-LO-phonon-emission and absorption processes are modeled by Froelich Hamiltonian. The dependence of the tunneling rate on the QW carrier density, temperature, barrier width between QW and QD, and energy difference between the QW state and the QD state are studied. The tunneling time ranging from several to a few tens of picoseconds are possible depending on the thickness of the barrier and the energy spacing between the QW and QD states.