National Repository of Grey Literature 10 records found  Search took 0.00 seconds. 
Laser spectroscopy of semiconductor quantum dots
Pokorný, Martin ; Trojánek, František (advisor) ; Kuldová, Karla (referee)
This work is focused on examining photoluminescent properties of InAs quantum dots (QDs) on GaAs substrate covered by GaAs1-xSbx strain reducing capping layer (SRL) prepared by Stranski-Krastanow method. We measured luminescence decay time of two samples with different concentration of Sb in this layer. We investigated the influence of temperature, intensity and wavelength of the excitation pulse on the luminescent decay time. We also compared the properties of the samples after excitation by 760 nm pulse and 850 nm pulse - the former one is energetically above the substrate band gap; in the second case we excited only the QDs and the wetting layer (WL). We consequently derived recombination and relaxation processes occurring inside InAs QDs and also the transport of charge carriers from the substrate and the WL into QDs. One part of this diploma thesis was to learn about the methods of measuring ultrafast photoluminescence and build the experimental set-up.
Nonlinear optical properties of silicon nanostructures
Žídek, Karel ; Trojánek, František (advisor) ; Bryknar, Zdeněk (referee) ; Kuldová, Karla (referee)
Název práce: Nelineární optické vlastnosti křemíkových nanostruktur Autor: Karel Žídek Katedra (ústav): Katedra chemické fyziky a optiky Vedoucí disertační práce: Doc. RNDr. František Trojánek, Ph.D. E-mail vedoucího: trojanek@karlov.mff.cuni.cz Abstrakt: Disertační práce se zabývá nelineárními optickými jevy a ultrarychlým vývojem luminis- cence křemíkových nanokrystalů. Pomocí metody optického hradlování signálu (časové rozlišení až 250 fs) porovnáváme ultrarychlý vývoj luminiscence křemíkových nanokrystalů s různými ve- likostmi (v řádu jednotek nanometrů) a také s rozdílnými formami pasivace. Pro nanokrystaly, kde po excitaci dominuje vliv zachytávání nosičů do povrchových stavů nanokrystalu, navrhujeme teoretický popis závislosti rychlosti těchto procesů na vlastnostech nanokrystalů. Dále v práci podrobně zkoumáme působení Augerovy rekombinace, která se projevuje jak v časově rozlišené, tak i v časově integrované emisi vzorků. Experimentální data velmi dobře popisuje námi navržený model na bázi kinetických rovnic. Závěr práce se zaměřuje na zkoumání ultrarychle dohasínající stimulované emise. U stávajících metod měření optického zisku (VSL a SES) navrhujeme jejich rozšíření pro...
Luminescence of quantum dot heterostructures in applied electric field
Kubištová, Jana ; Zíková, Markéta ; Kuldová, Karla ; Pangrác, Jiří ; Hospodková, Alice ; Hulicius, Eduard ; Petříček, Otto ; Oswald, Jiří
In this work, photoluminescence (PL) and electroluminescence (EL) of samples with InAs/GaAs quantum dots were measured with electric voltage or current applied on the structure. The EL structures emitting at 1300 nm were prepared by using n-type substrate. By applying the electric voltage in reverse bias on the sample, the evinced PL may be switched off - it decreases rapidly with the applied voltage and is negligible at about 10 V. Such structures which PL intensity is tunable by applied voltage have a broad spectrum of applications in optoelectronics.
In situ monitorování růstu MOVPE InAs/GaAs struktur s kvantovými tečkami pomocí reflektanční anisotropické
Vyskočil, Jan ; Hospodková, Alice ; Pangrác, Jiří ; Melichar, Karel ; Oswald, Jiří ; Kuldová, Karla ; Mates, Tomáš ; Šimeček, Tomislav ; Hulicius, Eduard
Reflectance anisotropy spectroscopy (RAS) has been used for the real-time observation and optimization of single and double InAs/GaAs quantum dot layer structure growth. The properties of samples were ex situ characterized by photoluminescence and AFM.
Studie InAs/GaAs kvantových teček vypěstovaných technologií LP-MOVPE
Hazdra, P. ; Atef, M. ; Komarnitsky, V. ; Oswald, Jiří ; Kuldová, Karla ; Hulicius, Eduard
We show simulation study of electronic transition energy for InAs/GaAs quantum dots fabricated with LP-MOVPE. The simulation results were compared with experimental data obtained by AFM and photoluminescence.
Lateral elongation of InAs/GaAs quantum dots studied by magnetophotoluminescence
Křápek, V. ; Kuldová, Karla ; Oswald, Jiří ; Hospodková, Alice ; Hulicius, Eduard ; Humlíček, J.
We have investigated single layer InAs QDs on GaAs substrate grown by MOVPE by means of magnetophotoluminescence up to 24 T. Fitting the field-dependence of band positions, we have found the ratio of lateral sizes within 1.5 –1.7, and the effective mass of 0.04 – 0.05.
MOVPE InAs/GaAs quantum dots with long-wavelength emission
Oswald, Jiří ; Kuldová, Karla ; Hospodková, Alice ; Hulicius, Eduard ; Pangrác, Jiří ; Mates, Tomáš ; Melichar, Karel ; Vyskočil, Jan
One method which enables the shift of photoluminescence spectra of InAs/GaAs quantum dots toward longer wavelengths is the covering of the dots by In.sub.x./sub.Ga.sub.1-x./sub.As strain reducing layer. With the increasing x we have observed the shift of PL maxima from 1.28 μm to 1.46 μm.
Vlastnosti vertikálně uspořádaných struktur kvantových teček
Hospodková, Alice ; Kuldová, Karla ; Hulicius, Eduard ; Oswald, Jiří ; Pangrác, Jiří
We have studied the overlap of electron wave functions of stacked QDs. We have found that for sample with the spacer thickness 15 nm the electron wave functions of QDs in stack are fully separated. We have found that for spacer thickness around 7 nm the electron wave functions of smaller QDs from deeper layers still overlap while the electron wave function of bigger QDs at top layers remain separated.
Characterization of lasers with ë-InAs layers in GaAs
Hazdra, P. ; Voves, J. ; Oswald, Jiří ; Hulicius, Eduard ; Pangrác, Jiří ; Melichar, Karel ; Šimeček, Tomislav ; Petříček, Otto ; Kuldová, Karla
The dependence of the electroluminescence spectra on the number of ë-InAs layers and on the distance of these ë-InAs layers was studied under pulse excitation in the wide range of current densities.

See also: similar author names
2 KULDOVÁ, Kateřina
2 Kuldová, Kateřina
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