Carrier heating in light-emitting quantum-dot heterostructures at low injection currents

Abstract

We present microscopic calculations of the light emission and carrier dynamics in an electrically pumped quantum-dot emitter at low injection currents and room temperature. The modeled structure consists of a bulk semiconductor and self organized InGaAs/GaAs quantum-dot layers ͑embedded by a wetting layer͒. Carrier transport through the structure is driven by scattering with longitudinal optical phonons including the nonequilibrium phonon dynamics. Even though the phonon distribution remains at room temperature, a substantial carrier heating corresponding to more than 50 K above the phonon temperature occurs in the wetting layer. Surprisingly, this temperature difference is observed in particular at low pump currents. It can be attributed to a nonequilibrium in the sample due to energy level alignment and external pumping.

Direct observation of spin-orbit splitting and phonon-assisted optical transitions in the valence band by internal photoemission spectroscopy

“…The potential barrier diverts the relaxation channel primarily through the SO band, which principally contributes to the yield outcome. Such a mechanism was also found in quantum-dot structures, 40 where carriers in the wetting layer with low kinetic energy (near the Ŵ point) are scattered into quantum dots. (Table II)a r e obtained as 794.8 ± 0.03 meV (GaSb) and 332.8 ± 0.3meV (In 0.53 Ga 0.47 As), which agree with the reported values of 796 meV (GaSb) 24 and 329.6m e V( I n 0.53 Ga 0.47 As).…”

Quantum light emission from cavity enhanced LEDs

“…Fig. 2(b): The QDs act as a sink for cold carriers, around the Γ-point of the bandstructure [7]. The heating is a result from a decreased number of cold carriers in the WL.…”

Theory of few photon dynamics in electrically pumped light emitting quantum dot devices

“…15,16 There are two basic scattering channels: i) relaxing carriers that translate their energy to other carriers via Coulomb interaction [17][18][19][20] and ii) carriers relax by emission of phonons. 15 The first case is important at high carrier densities, at low carrier density regime we focus on electron-phonon interaction: Phonon assisted relaxation from the continuous WL into the discrete QD states is a long discussed topic since longitudinal optical phonons have a nearly constant dispersion and direct step-like process -emitting one phonon each step-is energetically forbidden (cf. Fig.…”

“…15 A microscopic approach based on correlation expansion leads to Boltzmann like equations of motion. We include relaxation within the bulk material and the WL, respectively as well as transitions between both.…”