Publications by Alok Rudra | EPFL Graph Search

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The coupling of a prescribed number of site-controlled pyramidal quantum dots (QDs) with photonic crystal (PhC) cavities was studied by polarization and power-dependent photoluminescence measurements. The energy of the cavity mode could be readily tuned, m ...

The emission pattern of charged excitons in a semiconductor quantum dot (QD) is composed of a quadruplet of linearly polarized lines when a magnetic field is applied in a Voigt configuration. The orientation of the linear polarization of exciton emission i ...

Deterministic positioning single site-controlled high symmetric InGaAs quantum dots (QDs) in (111)B-oriented GaAs photonic crystal cavities with nanometer-scale accuracy provides an idea component for building integrated quantum photonic circuits. However, ...

This dataset corresponds to the following manuscript: Zendrini, M., Dubrovskii, V., Rudra, A., Dede, D., Fontcuberta i Morral, A., Piazza, V. “Nucleation-Limited Kinetics of GaAs Nanostructures Grown by Selective Area Epitaxy: Implications for Shape Engi ...

We present a model for the interplay between the fundamental phenomena responsible for the formation of nanostructures by metalorganic vapor phase epitaxy on patterned (001)/(111)B GaAs substrates. Experiments have demonstrated that V-groove quantum wires ...

We report on efficient, narrow linewidth exciton recombination in GaAs/AlGaAs V-groove quantum wire light-emitting diodes at room temperature. The high efficiency is due to a selective carrier injection mechanism resulting in an estimated internal quantum efficiency of similar to 20% with an electroluminescence (EL) linewidth as narrow as 15 meV. The thermal broadening contribution to the linewidth is 6 meV due to exciton scattering with optical phonons. An analysis of the EL peak shift in a magnetic field

We studied the formation of buried heterostructures obtained in a single growth step over nonplanar substrates patterned with ridges. When the ridge dimensions are large enough, the growth on the mesa top is similar to that on a planar substrate. In contrast, ridge spacings below almost-equal-to 10 mum influence the composition of the alloys grown on the ridge as well as those grown in the valley centre. The possible surface mechanisms which may explain this behaviour are discussed.

We present a detailed study of biexciton complexes formed in single, site-controlled pyramidal GaInAs/GaAs quantum dots (QDs). By using power dependent measurements and photon correlation spectroscopy, we identify the excitonic transitions of a large numbe ...

High quality InP/InGaAsP Distributed Bragg Reflectors (DBRs) are a key element in Vertical Cavity Surface Emitting Laser (VCSELs) for long wavelength (1.55 mu m) applications [1-3]. Because of the small index difference between InP and InGaAsP, more than 30 periods are needed to obtain reflectivities above 99 %, which makes it a challenge for the crystal growth technique. In this paper we present the structural and optical characteristics of such DBRs grown by Chemical Beam Epitaxy (CBE) at high growth rate

By using chemical beam epitaxy at growth temperatures as low as 460-480 degrees C, we have overcome strain relaxation problems that prevented so far the successful use of InAsP quantum wells in 1.55 mu m lasers. Five quantum well InAsP/InGaAsP horizontal cavity lasers showed 88% internal efficiency, 1.6 cm(-1) losses per well, and 33 A/cm(2) transparency current density per well, which equal or even surpass the best published characteristics for 1.55 mu m wavelength lasers based on any material system. More

Arrays of site-controlled, pyramidal InGaAs/GaAs quantum dots (QDs) grown by organo-metallic chemical vapour deposition with densities comparable to those of self-assembled QDs (5 x 109 cm(-2)) are demonstrated. The QDs exhibit high quality photoluminescen ...

We demonstrate selective optical coupling of multiple, site controlled semiconductor quantum dots (QDs) to photonic crystal waveguide structures. The impact of the exact position and emission spectrum of the QDs on the coupling efficiency is elucidated. Th ...

Interactions of site-controlled quantum dots with a high-order cavity mode of an L7-type photonic crystal cavity are resolved spatially and spectrally. We observed a spatial avoided crossing in polarization-resolved optical emission of quantum dots. ...

Photoluminescence intensity and emission wavelength of InAsP/InGaAsP and InGaAs/InGaAsP multi-quantum well (MQW) laser structures grown by chemical beam epitaxy (CBE) at 460 degrees C and V/III ratio of 2 are considerably affected by annealing at temperatures 600-650 degrees C which prevents lasing of these structures fused on GaAs substrates. It is shown that the degradation of luminescence characteristics can be decreased by increasing the growth temperature to 480 degrees C and V/III ratio to 4. InAsP/In

The fabrication and characterization of site-controlled InGaAs/GaAs quantum dots (QDs) made by MOVPE using triethylgallium (TEGa) on patterned {111}B GaAs substrates are reported. Results are compared to more traditional pyramidal QD structures grown emplo ...

When AxGa1-xAs layers are grown on V-grooved GaAs substrates by metal organic chemical vapour deposition (MOCVD), a Ga rich vertical quantum well (VQW) appears in the V-groove centre. The width and Ga enrichment of this structure depend on the nominal Al concentration and growth temperature. From EELS linescans and spectrum images, concentration profiles and maps of VQWs are obtained, and a subsequent bandstructure calculation shows up to three confined sublevels in the VQW. Carrier confinement in segments

Our interest is centred on the very thin layers consisting of only one or a few monolayers of InAs. The optical transition energies, measured by photoluminescence spectroscopy, are compared with theoretical calculations obtained in envelope function approximation and through an empirical tight-binding method. This comparison yields values for the not well-known valence band offset at the InAs/InP interface, and the luminescence lines observed at different energies could be assigned to layers between one and

We demonstrate the cavity quantum electrodynamics towards strong- coupling regime mediated by cavity loss and exciton pure dephasing in singular site-controlled quantum dotnanocavity system, studied by micro-photoluminescence (mu-PL) and time- resolved PL ...

Germanium nanowires could be the building blocks of hole-spin qubit quantum computers. Selective area epitaxy enables the direct integration of Ge nanowires on a silicon chip while controlling the device design, density, and scalability. For this to become ...

The results of a group theoretical analysis of the excitonic fine structure are presented and compared with spectroscopic data on single quantum dots. The spectral features reveal the signatures of a symmetry higher than the crystal symmetry (C-3v). A cons ...

Alok Rudra

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Ordered systems of site-controlled pyramidal quantum dots incorporated in photonic crystal cavities

Coulomb correlations of charged excitons in semiconductor quantum dots

Exciton-polariton dynamics of the single site-controlled quantum dot-nanocavity in the coexisting strong-weak coupling regime

Nucleation-Limited Kinetics of GaAs Nanostructures Grown by Selective Area Epitaxy: Implications for Shape Engineering in Optoelectronics Devices

Decomposition, diffusion, and growth rate anisotropies in self-limited profiles during metalorganic vapor-phase epitaxy of seeded nanostructures

Efficient, narrow linewidth excitonic emission at room temperature from GaAs/AlGaAs V-groove quantum wire light-emitting diodes

One-Step Growth of Buried Heterostructures by Chemical Beam Epitaxy over Patterned InP Substrates

Bound and anti-bound biexciton in site-controlled pyramidal GaInAs/GaAs quantum dots

Structural and optical characterization of InP/InGaAsP distributed Bragg reflectors grown by CBE

Low Threshold 1.55 µm Wavelength InAsP/InGaAsP Strained Multi-Quantum Well Laser Diode Grown by Chemical Beam Epitaxy

Dense arrays of pyramidal quantum dots with narrow linewidth photoluminescence spectra

Site-controlled quantum dots coupled to photonic crystal waveguides

Spatial Avoided Crossing in Optical Emission of Site-Controlled Pyramidal Quantum Dots in Photonic Crystal Cavities

Thermal Stability of InP-Based Structures for Wafer Fused Laser Diodes

Site-controlled InGaAs/GaAs pyramidal quantum dots grown by MOVPE on patterned substrates using triethylgallium

Use of quantitative EELS and cathodoluminescence for study of carrier confinement and diffusion in self organized vertical quantum wells

Optical study on ultrathin InAs/InP single quantum wells

Towards strong-coupling regime in singular site-controlled InGaAs quantum dots-nanocavities

Control of Ge island coalescence for the formation of nanowires on silicon

Symmetry Elevation and Symmetry Breaking: Keys to Describe and Explain Excitonic Complexes in Semiconductor Quantum Dots