title: Effect of Auger Recombination on Lasing in Heterostructured Quantum Dots with Engineered Core/Shell Interfaces.
abstract: Nanocrystal quantum dots (QDs) are attractive materials for applications as laser media because of their bright, size-tunable emission and the flexibility afforded by colloidal synthesis. Nonradiative Auger recombination, however, hampers optical amplification in QDs by rapidly depleting the population of gain-active multiexciton states. In order to elucidate the role of Auger recombination in QD lasing and isolate its influence from other factors that might affect optical gain, we study two types of CdSe/CdS core/shell QDs with the same core radii and the same total sizes but different properties of the core/shell interface ("sharp" vs "smooth"). These samples exhibit distinctly different biexciton Auger lifetimes but are otherwise virtually identical. The suppression of Auger recombination in the sample with a smooth (alloyed) interface results in a notable improvement in the optical gain performance manifested in the reduction of the threshold for amplified spontaneous emission and the ability to produce dual-color lasing involving both the band-edge (1S) and the higher-energy (1P) electronic states. We develop a model, which explicitly accounts for the multiexciton nature of optical gain in QDs, and use it to analyze the competition between stimulated emission from multiexcitons and their decay via Auger recombination. These studies re-emphasize the importance of Auger recombination control for the realization of real-life QD-based lasing technologies and offer practical strategies for suppression of Auger recombination via "interface engineering" in core/shell structures.
authors.affiliation: Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.|Center for High Technology Materials, University of New Mexico , Albuquerque, New Mexico 87131, United States.
authors.forename: Young-Shin
authors.initials: YS
authors.lastname: Park
authors.affiliation: Photo-Electronic Hybrids Research Center, National Agenda Research Division, Korea Institute of Science and Technology , Seoul 02792, Korea.
authors.forename: Wan Ki
authors.initials: WK
authors.lastname: Bae
authors.affiliation: Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Baker
authors.affiliation: Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Lim
authors.affiliation: Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Victor I
authors.initials: VI
authors.lastname: Klimov
keywords: Auger recombination; core/shell heterostructure; lasing; optical gain; quantum dot; semiconductor nanocrystal