Enhanced photoluminescence of colloidal nanocrystals embedded in epitaxially grown semiconductor microstructures

Abstract

Colloidal nanocrystals (NCs) integrated in epitaxially grown semiconductors provide a flexible alternative to Stranski-Krastanow quantum dots for many different optoelectronic applications such as low-threshold lasers or single-photon emitters. We studied the optical properties of various CdSe core-only and core/shell NCs integrated in ZnSe epitaxial-chemical hybrid structures. Depending on the type and environment of the NCs, a blueshift of the photoluminescence energy and a strong reduction of the emission intensity are observed after overgrowth. We demonstrate that these effects are caused by a potential barrier at the interface between NCs and ZnSe. The application of an appropriate postgrowth laser annealing procedure removes this potential barrier and enhances charge transfer from the ZnSe into the NCs. Consequently, we observe a significant increase of the emission intensity and a redshift of the photoluminescence energy of the NCs after annealing. Three-dimensional quantum-mechanical model calculations of the band diagram of the NCs as synthesized in solution, after overgrowth with ZnSe and after laser annealing confirm the presence of this potential barrier and its reduction due to the annealing.

CuO and Co3O4 Nanoparticles: Synthesis, Characterizations, and Raman Spectroscopy

“…Nanocrystalline semiconductor particles have drawn considerable interest in recent years because of their special properties such as a large surface to volume ratio, increased activity, special electronic properties, and unique optical properties as compared to those of the bulk materials [1,2]. Moreover, it has been shown that colloidal NCs can be integrated in epitaxial grown layers, which allows for the realisation of real device implementations based on NCs [3]. The oxides of transition metals represent an important class of semiconductors, which have applications in magnetic storage media, solar energy transformation, electronics, and catalysis [4].…”

Improving carrier injection in colloidal CdSe nanocrystals by embedding them in a pseudomorphic ZnSe/ZnMgSe quantum well structure

“…Although the PL blue-shift measured for embedded nanocrystals might be, in principle, qualitatively explained by the change of the quantum confinement owing to the replacement of an organic matrix by semiconductor ones, we consider that further systematic studies are needed to elucidate explicitly the origin of this remarkable feature. Preliminary theoretical models have been reported in [12,14,15].…”