Theory of carrier and photon dynamics in quantum dot light emitters

Abstract

We present a microscopic theory describing the charge carrier and light emission dynamics in quantum dot (QD) light emitters. The theory covers non-classical light emission (fluorescence and Raman emission) in the low carrier injection limit as well as laser emission and pulse amplification in the high carrier injection limit. The theoretical approach is based on QD Bloch equations including microscopically calculated Coulomb and electron-phonon scattering rates between bound QD, continuous wetting layer (WL) and bulk states. In the low carrier density limit, multi-phonon relaxation is the dominant process, while at high charge carrier densities, Coulomb scattering dominates the dynamics. Using an equation of motion approach, we address (i) time-resolved fluorescence and Raman emission, (ii) electrical injection and charge carrier transfer from bulk into WL and QD states, (iii) single photon emission and (iv) gain dynamics of QD amplifiers and lasing dynamics in QD vertical-cavity surface-emitting lasers (VCSELs) at high injection currents.

Precise shape engineering of epitaxial quantum dots by growth kinetics

“…Simple electronic quantum confinement considerations, in fact, indicate that the ability to control independently QD size and aspect ratio permits the independent control of QD emission energy and electronic interlevel energy spacing. The latter is extremely relevant in shaping electron-phonon interaction in QDs [59][60][61][62], a fundamental property of QDs for the improvement of quantum devices at room temperature [63,64].…”

Modeling of quantum dot lasers with microscopic treatment of Coulomb effects

“…In previous publications Dachner et al 2010) an approximation of this expression by contributions possessing a similar formal structure as the in-and out-scattering terms (first two lines) has been used, which leads to smaller dephasing times. For the numerical evaluation of Γ 2 in this paper all contributions in (11) have been considered.…”

“…Also the optical transitions between the QD electron and hole states, that result in the optical gain, will be modified by the Coulomb interaction. This is reflected by a density dependend dephasing time (Lorke et al 2006;Dachner et al 2010), which modifies the optical gain. The active region of our considered device comprises optically active QDs grown on a 2D WL as shown in Fig.…”

Quantum light emission from cavity enhanced LEDs

“…To simulate realistic operating points for devices, the interactions between electrons and holes confined in the QDs and the wetting layer must be taken into account. Therefore, we include Coulomb interaction in the emission process as well as electron-phonon coupling, considering multi-phonon processes based on an effective multiphonon Hamilton operator to calculate the quantum light emission on a microscopical level [6]. Here, we focus on the dynamics at low carrier densities, e. g. single photon emitter limit.…”