Dilute-Nitride Quantum Wires and Quantum Dots for Nanophotonic Applications

• Forschungsstelle: COST
• Projektnummer: C10.0123
• Projekttitel Englisch: Dilute-Nitride Quantum Wires and Quantum Dots for Nanophotonic Applications

Schlüsselwörter (Englisch)

Semiconductors; photonics; quantum wires; quantum dots; nanostructures; MOVPE; patterned growth; single photon emitters; lasers

Forschungsprogramme (Englisch)

COST-Action MP0805 - Novel Gain Materials and Devices Based on III-V-N Compounds

Kurzbeschreibung (Englisch)

See abstract

Weitere Hinweise und Angaben (Englisch)

Full name of research-institution/enterprise: EPF Lausanne Laboratoire de physique des nanostructures LPN EPFL SB IPEQ LPN, PH D3 425 (Bâtiment PH)

Partner und Internationale Organisationen (Englisch)

CH, CZ, DE, DK, EL, ES, FI, FR, IE, IL, IS, IT, LT, PL, PT, RO, TR, UK

Abstract (Englisch)

In this project, we explored the formation mechanisms and the optical properties of dilute-nitride InGaAsN/GaAs quantum wires (QWRs) and quantum dots (QDs) grown by organometallic vapor phase epitaxy (OMVPE) on nonplanar substrates. The objective was the development of novel semiconductor nanostructures for applications in lasers or single-photon emitters operating in the optical fiber telecommunication (1.3-1.55µm) wavelength window. The work relied on our previous studies of InGaAs/GaAs QWRs and QDs grown on V-grooved (100) GaAs substrates and (111)B GaAs substrates patterned with pyramid arrays. The main difficulty in this area is introducing sufficient (small) amounts of nitrogen into the InGaAs matrix without compromising the optical quality of the structures. The dilute nitride concentrations were introduced by employing a DMHz source in the OMVPE reactor, and at first the growth of InGaAsN/GaAs quantum well (QW) heterostructures was studied and optimized. High quality dilute-nitride QW structures were obtained by using a novel modulated-flux OMVPE, as attested to by the photoluminescence spectra of the structures. In the second phase of the project, InGaAsN/GaAs site-controlled QWRs were grown on (100) GaAs substrates patterned with V-grooves using the modulated-flux OMVPE technique. The structures were characterized using transmission electron microscopy, showing the formation of crescent-shaped wires at the bottom of the V-grooves. Photoluminescence (PL) studies allowed identification of efficient emission due to recombination at the QWRs. By proper adjustments of the growth conditions, QWR emission at 1.3µm wavelength at room temperature was achieved. Hydrogeneation of the dilute-nitride QWRs and magneo-PL studies helped to elucidate the process of nitrogen incorporation and assess the two-dimensional quantum confinement effects in the wires. In the last phase of the project, site-controlled InGaAsN/GaAs QDs were grown on (111)B GaAs substrates patterned with arrays of pyramidal pits produced using electron beam lithography. Evidence for incorporation of nitrogen and consequent red shift in the QD emission wavelength was provided by spectroscopy. Large inhomogeneous broadening, as compared with reference nitrogen-free, was observed and attributed to large fluctuations in nitrogen content from dot to dot. Single QDs were isolated using electron beam lithography and mesa etching, permitting the PL spectroscopy of single dilute-nitride QDs. Single exciton transitions were identified in the PL spectra of single QDs. Analysis of the polarization state of the emitted light showed that the symmetry of these QDs is significantly reduced as compared with the nitrogen-free reference dots, probably due to the strong perturbation of the crystal potential induced by the N atoms. This result provides interesting perspectives on the impact of nano-scale confinement in the case of highly diluted semiconductor alloys.

Datenbankreferenzen (Englisch)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C10.0123