Coulomb scattering with remote continuum states in quantum dot devices

Abstract

Electron capture and emission by Coulomb scattering in self-assembled quantum dot (QD) devices is studied theoretically. While the dependence of the Coulomb scattering (Auger) rates on the local wetting layer electron density has been a topic of intense research, we put special interest on the remote scattering between QD electrons and continuum electrons originating from a quantum well, doped bulk layers or metal contacts. Numerical effort is made to include all microscopic transitions between the Fermi distributed continuum states. The remote Coulomb scattering is investigated as a function of the electron density, the distance from the QDs and the temperature. Our results are compared with experimental observations, considering lifetime limitations in QD memory structures as well as the electron emission in pn-diodes

Coulomb Damped Relaxation Oscillations in Semiconductor Quantum Dot Lasers

“…These have to be captured into the bound QD states before the laser transition can take place. Since in the lasing regime, the WL carrier density is very high, the capture processes are dominated by Coulomb scattering (nonlocal Auger recombination) [23], [25], [26], which is also supported by the modeling of QD transport experiments [27], [28]. Our approach also includes the electron-phonon scattering for the cooling process in the WL, but neglects it for scattering into the QD states.…”

“…We consider a two-level system for electrons and holes in the QDs, since the carrier relaxation processes within the WL and within the QD states are much faster (∼1 ps) than capture processes from the WL into the QDs at high WL carrier densities [23]. As a result, only the energetically lowest electron and hole levels in the QDs contribute crucially to the laser dynamics [20].…”

Unbound states in quantum heterostructures

“…They found this Auger relaxation to become efficient (transition rate in excess of 10 11 s -1 ) only for large plasma concentration (10 11 cm -2 ). A similar calculation was undertaken by Wetzler et al [72] who studied the case of Auger processes between the electrons bound to a QD and 2D (electrons in a wetting layer, a nearby QW) or 3D (contacts) delocalized carriers located a Fig. 15 Sketch of the perturbation schemes that contribute to the Auger or phonon broadening of an excited transition (here P e -P h ) superimposed to a crossed continuum (here S e -m h ) distance d from the QD plane.…”

Theory of Nonlinear Transport for Ensembles of Quantum Dots

“…A more detailed analysis of the Auger recombination rates for quantum dots spatially separated from free electron states acting as scattering partner was presented in [21]. Again, screening is an important issue, which has to be treated in detail for the complex geometry involved.…”