Project name

Project name: Growth and modelling of distributed Bragg reflectors for quantum microcavities

Contract no. 31/05.10.2011

Project code: PN-II-RU-TE-2011-3-0070

PN II Program Name: Human Resources

Subprogram: Research projects for the stimulation of the forming of young independent research teams

Contracting authority: Executive Agency for Higher Education, Research, Development and Innovation Funding

Project director: Flavian STOKKER-CHEREGI

Coordinator: National Institute for Lasers, Plasma, and Radiation Physics

Project summary:
The prediction of room-temperature polariton lasing in quantum microcavities (MCs), as a result of Bose-Einstein condensation of polaritons, is an alluring achievement that has triggered widespread interest in the design and realization of such structures. Although significant advances have been reported in the theory and realization of MCs with different types of active media (bulk semiconductors, organic, hybrid, quantum wells, quantum dots, etc.) exhibiting polariton luminescence properties, so far no structures of such sort having practical application have been achieved. This project addresses several issues related to the design and execution of distributed Bragg reflectors (DBRs), which are a crucial element in the realization of MCs exhibiting polariton lasing properties. A team of five young researchers (2 Doctors and 3 PhD students) will work over a 36-month period on: i) modeling the design of DBRs using computer code based on the transfer matrix theory; ii) growing these structures by pulsed laser deposition (PLD) and plasma beam assisted PLD; iii) providing feedback on the quality and characteristics of samples by analyzing their optical (reflectivity and spectroelipsometry), morphological (atomic force microscopy), and compositional (secondary ion mass spectrometry) properties. Our goal is the realization of state-of-the-art DBRs by means of PLD, which is a fully 'green' alternative to molecular beam epitaxy and chemical vapour deposition growth techniques.

Project objectives:

The general objective of our project is the realization of high quality factor (Q) DBRs (in excess of several hundreds), with controlled dopings, for different types of microcavities. The types of microcavity structures, compatible with a room-temperature polariton lasing regime, for which we will consider the design and realization of DBRs, are semiconductor microcavities, with either bulk or quantum well active medium.

The scientific and technological objectives we need to achieve in order to reach our final goal are the following:

· A comprehensive approach towards the design and modeling of the DBRs for semiconductor microcavities using the transfer matrix theory that takes into account the effects of: i) wavelength dependence of the material optical coefficients; ii) broadening induced by the presence of doping agents; iii) possible variation of the optical coefficients due to the presence of dopants.

· Growth of high Q DRBs with controlled doping by means of PLD and plasma beam assisted PLD, resulting in structures adapted for various types of bulk and quantum well based semiconductor microcavities exhibiting polariton lasing properties. Deliverables: DBR structures / prototypes.

· Compositional analysis, study of the surface and interface morphology, characterization of stop band and reflectivity, determination of averaged optical coefficients by correlating results from secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM) and spectroelipsometry measurements. Additionally, scanning electron microscopy and X-ray diffraction analysis can be performed, should there be a particular need for such characterizations. The feedback from these results will be used both for the adjustment of growth conditions in order to further optimize the overall quality of the DBRs, as well as for the improvement and fine tuning of the computer code running the transfer matrix theory simulations. Generated knowledge: scientific publications.

Dissemination:

1) article: F. Stokker-Cheregi, A. Nedelcea, F.M. Voicu, D.M. Marin, R. Birjega, M. Dinescu, "Structure and morphology of indium nitride thin films grown by plasma assisted PLD: the impact of nitrogen flow and substrate temperature", Romanian Reports in Physics, Vol. 65, No. 1, P. 213–218, 2013
2) poster: F. Stokker-Cheregi, G. Epurescu, D. Colceag, V. Ion, A. Andrei, R. Birjega, M. Dinescu, "Optical properties of ZnO and MgZnO thin films as a function of thickness and Mg content", EMRS 2012 - Spring Meeting, Symposium V
3) poster: F. Stokker-Cheregi, D. Marin, A. Nedelcea, D. Colceag, V. Ion, R. Birjega, M. Dinescu, "Structure, morphology, and optical properties of InN and AlN nanostructures obtained by laser techniques", EMRS 2012 - Spring Meeting, Symposium V
4) poster: F. Stokker-Cheregi, D.-M. Marin, C. Ghica, M. Dinescu, "Optical and compositional characterization of InN and AlN particles produced by laser ablation of bulk metal targets immersed in liquid nitrogen", EMRS 2013 - Spring Meeting, Symposium V
5) article: D.-M. Marin, F. Stokker-Cheregi, M. Dumitru, V. Ion, M. Dinescu, "Aluminium nitride thin films grown by plasma assisted pulsed laser deposition", Romanian Reports in Physics, vol. 66, No. 4, P. 1118–1124, 2014
6) article: F. Stokker-Cheregi, A. Matei, M. Dinescu, C.E. Secu, M. Secu, "Photoluminescence of Eu-doped LiYF4 thin films grown by pulsed laser deposition and matrix-assisted pulsed laser evaporation", JOURNAL OF PHYSICS D-APPLIED PHYSICS 47, 045304 (2014)
7) poster: F. Stokker-Cheregi, A. Matei, M. Dinescu, C. E. Secu, M. Secu, "Er/Yb doped LiYF4 thin films obtained by pulsed laser deposition of a silica xerogel", EMRS 2014 - Spring Meeting, Symposium J

First stage - 15.12.2011 (click for the scientific report)

Value of first stage: 90,000 lei

Second stage - 15.12.2012 (click for the scientific report)

Value of second stage: 225,600 lei

Third stage - 15.12.2013 (click for the scientific report)

Value of third stage: 225,600 lei

Fourth stage - 30.09.2014 (click for the scientific report)

Value of third stage: 171,600 lei