Distributed Bragg reflectors obtained by combining Se and Te compounds: Influence on the luminescence from CdTe quantum dots

Abstract

We report on the optical properties of structures containing self assembled CdTe quantum dots (QDs) combined with Te and Se based distributed Bragg reflectors either in a half cavity geometry with a relatively broad cavity mode or in a full cavity geometry where the cavity mode is much narrower. We show that for both structures the extraction coefficient of the light emitted from the QDs ensemble is enhanced by more than one order of magnitude with respect to the QDs grown on a ZnTe buffer. However, a single QD line broadening is observed and attributed to an unintentional incorporation of Se in the vicinity of the CdTe QDs. We show that postponing the QDs growth for 24 h after the distributed Bragg reflector deposition allows recovering sharp emission lines from individual QDs. This two step growth method is proven to be efficient also for the structures with CdTe QDs containing a single Mn2+ ion.

Semiconductor devices for entangled photon pair generation: a review

“…However, in the case of entanglement generation via the biexciton-exciton cascade, Purcell enhancement is a limited resource. Indeed, the biexciton photon and the exciton photon, in general, have different frequencies so only moderate quality factors can be chosen in order to keep both frequencies within the resonance of the cavity [202]. Figure 22: Double-micropillar structure, also called 'photonic molecule'.…”

“…However, in the case of entanglement generation via the biexciton-exciton cascade, Purcell enhancement is a limited resource. Indeed, the biexciton photon and the exciton photon, in general, have different frequencies so only moderate quality factors can be chosen in order to keep both frequencies within the resonance of the cavity [202]. A further substantial improvement of the extraction efficiency of entangled photons was obtained by Dousse et al by etching a double-micropillar structure out of a semiconductor planar microcavity, the quantum dot being in one of the two pillars [161] (Figure 22).…”

Interaction of Te and Se interlayers with Ag or Au nanofilms in sandwich structures

“…The intensity of the modified Lorentz band [37] centered at 275–300 nm decreased while the intensity of the bands from 325 to 400 nm increased. The latter are connected to the roughness of the layer (so the intensity would naturally increase with increased roughness) [26], but also to the interband transitions at the L-point in the Brillouin zone, while the former is connected to the interband transitions at the X-point in the Brillouin zone [38–39]. As the carriers at the X-point have a negative effective mass along one direction (X–Γ) and the carriers at the L-point have a negative effective mass along two opposite directions (L–X and L–K), the microstrain on metal grains would directly translate into changes in the intensity of the interband transitions and possible shifts in their energy, which is what we observe.…”

“…The purity of sublimated ingots for both Te and Se was 7N. To avoid cross-contamination during the deposition of Te or Se only one Knudsen cell was kept at working temperature [39]. SiO 2 , Ag and Au, LiF layers were deposited from fabmate or tungsten crucibles using a PVD75 Lesker e-beam evaporator.…”

Antireflective Photonic Structure for Coherent Nonlinear Spectroscopy of Single Magnetic Quantum Dots

“…Recently, the same material system was used for the growth of Mn-doped QDs on the top of 10 DBR pairs. The process was carried out using a single MBE machine, but growth interruptions were anyway required to clean the chamber from the residual Se atoms, which incorporated into QDs and impaired their optical properties [36].…”