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Tuning of MBE growth of AlGaInAs-based microcavities with embedded QDots or QWells

Tomasz Slupinski ,  Piotr Stawicki ,  Barbara Pietka ,  Katarzyna Golasa ,  Jean-Guy Rousset ,  Wojciech Pacuski ,  Adam Babinski ,  Jacek Szczytko ,  Jerzy Łusakowski 

Faculty of Physics, University of Warsaw, Hoża 69, Warszawa 00-681, Poland

Semiconductor microcavities with a high quality factor grown by MBE require high technological precision and knowledge of how optical constants of materials used change with temperature from a growth one to a  measurement one (e.g. from ~900K to ~4K in case of AlGaAs). High quality microcavities enable studies of quantum cavity electrodynamics or are used in optoelectronics. By embedding quantum wells (QWells) or dots (QDots) in a microcavity the control of spontaneous emission is possible (Purcell effect) or a strong coupling of photons and excitons leading to a normal mode splitting (exciton polaritons) can be observed if the cavity quality factor is high enough. Optically active QDots emit light in a wider wavelength range than QWells, comparable to a shift of cavity mode’s wevelength with temperature from growth one to low one, and so the optically active microcavity with QDots is easier to prepare epitaxially.  

We present GaAs-AlAs-based microcavities growth by molecular beam epitaxy (MBE) with built-in InAs self-assembled QDots or InGaAs QWells. The Bragg mirrors are made of GaAs (high refractive index) and AlAs (low refractive index) λ/4 layers, the cavity is made of GaAs of λ width. We concentrated on a proper tuning of cavity mode’s wavelength to the emission wavelength of QDots or QWells.  We use modeling of optical properties of  microcavities by the transfer matrix method taking into account a temperature dependence of refractive indexes of GaAs and AlAs materials reported in literature. We test growth procedures which take into account this temperature dependence of optical constants and try to minimize the limitations of MBE technology, like flow of molecular beams intensity over microcavity growth time. Properties of QWells embedded are modeled using NextNano software. Emission and reflectivity measurements from InAs QDots or InGaAs/GaAs QWells in GaAs-AlAs microcavities grown will be presented and discussed.   

As an example we present in the Figure a high-resolution image of photoluminescence at low temperature T=4K, which illustrates dispersion of the cavity mode for light emitted by InAs QDots built-in in GaAs/AlAs microcavity. We observe that the emission from the cavity with QDots in wavevector space is composed of a number of discrete states laid along the dispersion curve. The number and shape of discrete states depend on a place in the sample probably indicating that the localized states are formed due to the imperfections of growth.


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Related papers

Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 8, by Tomasz Slupinski
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-15 22:33
Revised:   2013-07-19 23:46