Search

Reference LPN-ARTICLE-1998-004doi:10.1049/el:19981148View record in Web of Science Record created on 2008-02-29, modified on 2017-12-03

1.52 µm double fused InGaAsP/AlGaAs vertical cavity surface emitting lasers with in situ built-in lateral current confinement were fabricated using a localised wafer fusion process. A threshold current of 2.5 mA at 4 V was obtained for devices with a 10 × 10 µm2 current aperture. These devices operate CW up to 30°C. The width of the dominant mode is less than 0.1 nm and the sidemode suppression ratio is 30 dB.

Chemical beam epitaxy (CBE) grown InAsP/InGaAsP edge-emitting laser diodes on GaAs substrates obtained by localised fusion in a nitrogen environment exhibit high quality fused interfaces. A degradation of fused lasers is observed which is attributed to the disordering of quantum wells at fusion temperatures induced by point defects incorporated during low temperature growth.

The intermixing process of ultrathin InAs/InP strained quantum well structures by thermal annealing at 730–830 °C is investigated by photoluminescence measurements. Analyzing the results using a microscopic model, the interdiffusion process is characterized by an activation energy close to 3.8±0.2 eV, leading to an interdiffusion coefficient close to 7±0.5×10−17 cm2/s at 830 °C.

The crystallographic structure of crater-containing oriented overgrowths on GaAs epitaxial layers grown by metalorganic vapor phase epitaxy (MOVPE) has been studied by transmission electron microscopy and diffraction. The craters are the visible outward sign of polycrystalline constructions of 6 grains or more having low order twin relations with the matrix. Anisotropic development of the facets of the grains is proposed to be the growth mechanism of the hillock. Stacking fault pyramids are present but their correlation with craters and overgrowths is not systematic.

In chloride vapour phase epitaxy of GaAs, it is known that the growth velocity depends on the cr stallographic face. Two orders of magnitude_difference in growth rate could occur between {111}Ga and {111}Aa. SO far, these features are strongly supported by the analysis of orientational dependence of the growth rate associated with surface kinetics. It is assumed that a dynamic equilibrium between the growing surfaces and the gas phase occurs, and the rate limiting process was shown to be the desorption of chlorine via hydrogen at the steps (1).

Reference LPN-ARTICLE-2002-003doi:10.1016/S0022-0248(01)02297-7View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

We report on an experimental study of the optical properties of modulation-doped V-groove semiconductor quantum wires. The Fermi-edge singularity is observed in emission and only weakly in absorption spectra. The conditions necessary for its observation are assessed by varying the electron density and providing the occupation of one, two or three one-dimensional (1D) subbands. We show that the existence of a strong optical singularity is related to both the effect of the hole localization and that of an enhancement induced by Coulomb correlations with a resonance associated with a partially empty 1D subband.

Quasi-one-dimensional AlGaAs quantum wires (QWRs) with parabolic heterostructure profiles along their axis were fabricated using metallorganic vapor phase epitaxy (MOVPE) On patterned (111)B GaAs substrates. Tailoring of the confined electronic states via modification in the parabolic potential profile is demonstrated using model calculations and photoluminescence spectroscopy. These novel nanostructures are useful for studying the optical properties of systems with dimensionality between zero and one. (C) 2014 Elsevier B.V. All rights reserved.

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 employing trimethylgallium (TMGa). Several potential advantages of the use of TEGa are demonstrated, including more reproducible achievement of QD transitions with narrow (< 100 mu eV) linewidths and better spectral uniformity across patterned substrates. These features are important for QD integration in optical cavities, which require both site and spectral stringent control. (C) 2014 Elsevier B.V. All rights reserved.

Pyramidal, site-controlled InGaAs/AlGaAs quantum dots (QDs) are studied by micro-photoluminescence (PL) spectroscopy in a magnetic field. The light-hole (LH) excitonic transitions exhibit diamagnetic shifts similar to those of their heavy-hole (HH) counterparts. From the evolution of the excitonic lines, effective g-factors of g = 1.7 and 0.4 for HH and LH neutral excitons are inferred. (c) 2007 Elsevier B.V. All rights reserved.

Low-threshold lasing is experimentally achieved for the first time in semiconductor photonic-crystal nanocavities embedding site-controlled quantum wires. The effect is established via direct observation of the stimulated emission in the time domain.

We report on the growth of barrier, reservoir and quantum well electron transfer (BRAQWET) structures using chemical beam epitaxy. The photoluminescence spectra of the structures are affected by the bias voltage. The QW emission line is extinguished at positive bias and the barrier emission line is extinguished at negative bias. These effects might be used for the BRAQWETs characterization.

We demonstrate engineering of carrier states in the conduction band (CB) and valence band (VB) of site-controlled InGaAs/GaAs quantum dots (QDs) grown into pyramidal recesses, by controlling their shape, size, and composition. QDs with CB level separation ranging from ∼15 to 70 meV are obtained, useful in applications based on intraband transitions, e.g., QD photodetectors and QD cascade lasers. Moreover, by varying the aspect ratio and composition of the QDs we are able to switch the polarization of the dominant interband transition, a feature of interest for producing single photon emitters and QD amplifiers with prescribed polarization states

We show that far off-resonance exciton-photon coupling reported for self-assembled quantum dots in optical microcavities is not universal, and demonstrate that site-controlled dots exhibit clean phonon-mediated resonant coupling.

Deterministic integration of site-controlled quantum dots with photonic crystal waveguides is demonstrated, which allows positioning the dots for optimal overlap with the waveguide modes. The coupling efficiency (β-factor) of quantum dot emission to propagating waveguide modes ranging from 0 to 88% is measured accounting for statistical variations of quantum dot properties. Using site controlled quantum dots permits us to distinguish between the spectral and spatial origins of fluctuations in β. The role of Fabry-Perot modes that prevent reaching a deterministic coupling between quantum dots and photonic crystal waveguides is revealed, and ways to overcome this problem are proposed. The results are useful for constructing high-flux single photon emitters based on multiplexed single photon sources.

Keywords: CRYSTALLOGRAPHIC PROPERTIES ; X-RAY ; INP ; INGAAS Note: Ecole polytech fed lausanne,inst appl phys,dept phys,ch-1015 lausanne,switzerland. Carlin, jf, ecole polytech fed lausanne,inst micro & optoelectr,dept phys,ch-1015 lausanne,switzerland.ISI Document Delivery No.: EY072Times Cited: 10Cited Reference Count: 11Cited References:ASONEN H, 1990, J CRYST GROWTH, V105, P101BASS SJ, 1986, J CRYST GROWTH, V79, P378BASSIGNANA IC, 1989, J APPL PHYS, V65, P4299FERRARI C, 1988, J APPL PHYS, V63, P2628GOETZ KH, 1983, J APPL PHYS, V54, P4543HALLIWELL MAG, 1984, J CRYST GROWTH, V68, P523KAWAGUCHI Y, 1986, 18TH C SOL STAT DEV, P619MACRANDER AT, 1987, J ELECTROCHEM SOC, V134, P1248MATSUI Y, 1985, J VAC SCI TECHNOL B, V3, P528RAZEGHI M, 1989, MOCVD CHALLENGE, V1TSANG WT, 1986, APPL PHYS LETT, V49, P170 Reference LOEQ-ARTICLE-1991-012doi:10.1016/0022-0248(91)90609-9 Record created on 2007-08-31, modified on 2017-05-12

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

The fabrication of defect-free and continuous transitions between AlGaAs/GaAs quantum wells (QWs) and quantum wires (QWRs) using organo-metallic vapor phase epitaxy on variable-width V-grooved substrates is demonstrated. The basic idea of our approach is developed using a Monte-Carlo simulation of the self-limiting growth on tapered grooves. A detailed surface and cross-sectional atomic force microscopy study reveals the high quality of the resulting coupled quantum structures. In particular, we demonstrate the efficient control, brought about by this experimental technique, on the well-wire transitions.

values of the conductance steps are suppressed. Our results suggest that a poor coupling between the 1D states of the wire and the 2D states of the reservoirs outside the gated region is responsible for the conductance suppression for strong lateral confinement. @S0163-1829~99!50516-X# In this paper we report the results of electron-transport measurements in V-groove GaAs/AlxGa12xAs quantum wires ~QWR's!. With these structures, it is possible to con- trol the strength of the lateral quantum confinement, thus allowing the comparison between nearly adiabatic and more abrupt transitions between the wire and the reservoir regions. In the ballistic transport regime, obtained for wires shorter than ;1.5 mm, we observe a systematic increase in the de- viation of the conductance steps from G 0 as the strength of the lateral confinement increases. Our data support recent models 7,9 assigning these deviations to electron scattering at

Reference LPN-ARTICLE-2000-004doi:10.1016/S0921-5107(99)00553-XView record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

Reference LPN-ARTICLE-2002-007doi:10.1016/S1386-9477(01)00286-7View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

The authors present low voltage barrier p-InP/p-GaAs junctions obtained by localised fusion which facilitates a better evacuation of absorbed gases and native oxides from the fused interface. Using this approach InGaAs/lnGaAsP/InP edge emitting lasers fused to p-GaAs were realised for the first time, showing better parameters than as-grown diodes. The presented results prove that localised fusion is a suitable tool for achieving additional lateral current confinement, which may be important for a wide variety of other device applications.

We demonstrate the self-formation of hexagonal nanotemplates on GaAs (111)B substrates patterned with arrays of inverted tetrahedral pyramids during metal-organic vapor phase epitaxy and its role in producing high-symmetry, site-controlled quantum dots (QDs). By combining atomic force microscopy measurements on progressively thicker GaAs epitaxial layers with kinetic Monte Carlo growth simulations, we demonstrate self-maintained symmetry elevation of the QD formation sites from three-fold to six-fold symmetry. This symmetry elevation stems from adatom fluxes directed towards the high-curvature sites of the template, resulting in the formation of a fully three-dimensional hexagonal template after the deposition of relatively thin GaAs layers. We identified the growth conditions for consistently achieving a hexagonal pyramid bottom, which are useful for producing high-symmetry QDs for efficient generation of entangled photons.

Exciton transfer between two parallel GaAs V-groove quantum wires (QWRs) or two planar quantum wells (QWs) separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence (PL) and PL excitation (PLE) spectroscopy. It is found that the transfer is strongly reduced between the widely spaced QWRs as compared with QWs. We have also investigated the optical absorption in single QWRs embedded in an AlGaAs V-shaped channel waveguide. Using a combination of PLE and absorption measurements we construct the full dependence of absorption spectra on the linear polarization. Our studies reveal the importance of inter-subband mixing in determining the energies of the light-hole-like transitions and thus the QWR absorption. Finally we present recent results on the fabrication and structural characterization of GaAs and GaP nanowires (NWs) grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates, using Au-catalyzed vapor–liquid–solid growth technique. It is shown that, apart from optimizing the NW growth parameters, substrate material and the procedure for preparing the substrate before the MBE growth play an important role in controlling the NWs.

The quantum-confined Stark effect (QCSE) in one-dimensional (1D) structures is expected to display enhanced transfer of oscillator strength and enhanced Stark shifts compared with two-dimensional (2D) systems. 1D quantum wires (QWRs) are, however, characterized by a 2D confinement potential that may have important consequences: the QCSE thus becomes two dimensional (2D-QCSE). Here we report an experimental and theoretical investigation of the 2D-QCSE in V-groove QWRs. We observe the 2D-QCSE and find striking effects due to electron or hole wave-function splitting. Furthermore, interplay of electric field, geometry and valence band mixing gives rise to new tunable features in polarization anisotropy.

Entangled photons are efficiently generated from highly symmetric, site-controlled InGaAs/GaAs quantum dots grown in inverted pyramids. Fine-structure splitting of the intermediate exciton level is suppressed without the application of electric, magnetic or strain fields. Polarization entanglement is demonstrated by measurements of the two-photon density matrix and the confirmation of several entanglement criteria.

A high-reflectance GaInP/GaAs distributed Bragg reflector (DBR) was grown by chemical beam epitaxy (CBE). The mirror consists of 40 pairs of alternating layers and was designed for a centre wavelength of 980 nm, resulting in a total thickness of 5.8 mum. Highly stable growth conditions led to a maximum reflectance of 0.99 and to a variation in the centre wavelength of only 5 nm over the 2'' (50.8 mm) wafer. Transmission electron microscopy and X-ray diffraction measurements confirmed the vertical uniformity and the crystallographic quality of the sample.

Reference LPN-ARTICLE-2000-013doi:10.1016/S1386-9477(00)00052-7View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

Based on site- and energy-controlled quantum wires (QWR) and quantum dots (QD), diverse photonic-crystal microcavity laser systems are proposed and discussed. Results demonstrating QWR lasing, cavity coupling and QD ordered arrays are presented.

An experimental method for accurate measurements of the reflectivity spectrum of mirrors is presented. It combines the noise reduction obtained with multiple beam reflections on two identical mirrors; high-beam quality, owing to the use of single-mode optical fibers; and high immunity against intensity variations of the beam. This method is demonstrated for characterizing a 30-period GaAs/Al(0.65)Ga(0.35)As distributed Bragg reflector designed for long-wavelength vertical-cavity surface-emitting lasers. Its peak reflectivity is found to be 99.43 ? 0.04% at 1.562 mum, and an optical absorption coefficient of alpha = 36 ? 6 cm(-1) is derived. The peak internal reflectivity of this distributed Bragg reflector used as the top mirror in a wafer-fused vertical-cavity surface-emitting laser is calculated to be 98.87 ? 0.12%, and the transmission is 0.28%.

Strong optical confinement implemented with 2D photonic-crystal (PhC) microcavities provides a powerful tool for controlling the features of light-matter interaction. Combined with nanostructures such as quantum wells, quantum wires (QWRs) or quantum dots, the PhC cavities — efficiently controlling spontaneous emission [1] — are envisaged to bring superior semiconductor-laser performance [2], which could be exploited for applications in low-power-consumption integrated optoelectronics. Furthermore, inter-cavity optical coupling may allow for optimizing the laser output power [3] and realizing ultra-fast switching devices [4]. Here, we present experimental and numerical studies of directly coupled L 3 -type PhC microcavities that employ monolithically embedded site-controlled QWRs acting as local internal light sources. Using microphotoluminescence (PL) experiments [5], it is shown that such PhC system supports coupled modes with distinct resonant wavelengths and delocalized optical fields. It is also demonstrated that the cavity losses of these modes may “split” as well, in general. Furthermore, we demonstrate single-mode QWR-PhC microlasers. Low thresholds (∼1 µW) and relatively high spontaneous-emission coupling factors (β ∼ 0.3) are achieved. Lasing is established based on power-dependent linewidth narrowing [6] and time-resolved photon dynamics [7]. This work provides grounds for the development of more complex PhC systems for experiments in quantum physics [8] and microlasers [4].

In this study, we present a systematic investigation of the emission spectra of excitonic complexes confined in QDs when an external magnetic field is applied in a direction perpendicular to the optical wave vector Voigt configuration. The effective g factors of an electron and a hole in individual QDs are obtained on the basis of a consistent analysis of the Zeeman splittings in many QDs. Our results reveal a large uniformity of the electron g factors but a broad variation in hole g factors when analyzing QDs emitting at nearly the same energy. By comparing the polarized emission spectra from the neutral and charged excitons in the same QD, we evidence a significant modification of the carrier g factors that we attribute to Coulomb correlations within the few-particle excitonic complexes. We use pyramidal In0.1Ga0.9As/Al0.3Ga0.7As QDs that allow us to observe simultaneously the positively and the negatively charged excitons in the same photoluminescence

We report on carrier-induced effects on emission and absorption in forward biased GaAs/AlGaAs V-groove quantum wire (QWR) diodes observed using low-temperature (10 K) photoluminescence (PL), electroluminescence (EL) and PL excitation (PLE) spectroscopy. In the case of simultaneous electron-hole injection we observe a band-gap renormalization (BGR) of at least 5 meV for a carrier density of approximate to 10(6) cm(-1), by comparing high-density EL spectra with low-density PLE spectra. In the case of electron injection of approximate to 10(6) cm(-1) we observe a complete quenching of the PLE absorption edge related to a Burstein-Moss shift of approximate to 35 meV. Hole band-filling is much less effective due to smaller subband spacing and larger density-of-states in the valence band.

Semiconductor quantum-dot (QD) systems offering perfect site control and tunable emission energy are essential for numerous nanophotonic device applications involving spatial and spectral matching of dots with optical cavities. Herein, the properties of ordered InGaAs/GaAs QDs grown by organometallic chemical vapor deposition on substrates patterned with pyramidal recesses are reported. The seeded growth of a single QD inside each pyramid results in near-perfect (

Demonstration of a terahertz quantum cascade laser grown by a low-pressure metalorganic vapor phase epitaxy is reported. The structural analysis of the grown structure shows a very high degree of vertical uniformity and sharp interfaces. Lasing emission at λ=90μm up to 93K with a threshold current density Jth=330A∕cm2 at 7K was obtained in a structure incorporating a single plasmon waveguide.

We have evaluated the structure of high-reflectivity InP/InGaAsP distributed Bragg reflectors grown by chemical-beam epitaxy at a growth rate of 3 mu m/h. Transmission electron microscopy combined with electron energy loss spectroscopy indicate lateral fluctuations in the GaInAsP alloy composition, clearly visible in the 490-510 degrees C growth temperature range, but less perceptible between 460 and 480 degrees C. In the higher temperature range, the modulation in composition shows a higher frequency along the [1 (1) over bar 0] direction than along [1 1 0].

We propose and investigate a new type of photonic crystal (PhC) cavity for integrated quantum photonics, which provides tailored optical modes with both confined and extended spatial components. The structures consist of elongated PhC cavities in which the effective index of refraction is varied quasi-linearly along their axis, implemented by systematic lateral shifts of the PhC holes. The confined modes have approximately Airy-function envelopes, exhibiting single peaks and extended tails, which is useful for optimizing single photon extraction and transmission in integrated quantum photonic devices. The measured spectrally resolved near-field patterns of such devices show the expected spatial and resonance wavelength behavior, in agreement with numerical simulations of the Airy-Bloch modes. The effects of fabrication-induced disorder on the mode features are also analyzed and discussed. Selective excitation of specific Airy-Bloch modes using integrated, site-controlled quantum dots as localized light sources is demonstrated. Based on the tilted-potential cavity, multiple-QD single photon emitters exploiting wavelength division multiplexing are proposed. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

We present results on the polarization-resolved photoluminescence emitted from InGaAs/AlGaAs single quantum dots (QDs) grown in inverted tetrahedral pyramids. The emitted light was detected for two mutually perpendicular linear polarization directions in the less conventional cleaved-edge geometry, in addition to the standard top-emission geometry. Whereas the in-plane linear polarization was isotropic, as a consequence of the high symmetry of the system, we found a strong polarization anisotropy of the edge-emitted light revealing QD states of predominantly heavy- or light-hole character. By temperature control of the charge state, several neutral and charged light-hole like exciton complexes were identified. In particular, a biexciton showing a twofold radiative recombination path, leading to two nearly perpendicularly polarized emission multiplets, was identified. These results are also of technological relevance for any design of optoelectronic QD-integrated devices.

We discuss the growth of lattice matched GaInAs, GaInAsP and GaInAsP/GaInAs multiple quantum well structures for high speed laser applications. Optical cavities, including five 90 angstrom GaInAs quantum wells with GaInAsP barriers and waveguides showed a 4 K photoluminescence line width of 8.7 meV. Transmission electron microscopy and X-ray diffraction confirm the good control over the growth of these structures.

Remote coupling between quantum emitters is of great importance for constructing quantum networks. Conventionally, this can be achieved via photon exchange by incorporating the quantum emitters in a waveguide or a large cavity. However, such photonic structures suffer from low quality-factors or large mode volumes, limiting the efficiency of light–matter interaction. Here, we demonstrate remote coupling between two site-controlled semiconductor quantum dot emitters mediated by an optical Fano resonance induced by coupling cavity modes via a continuum waveguide state. Unlike ordinary coupled modes, the Fano mode offers both a spatially extended field and a high local density of optical states at the emitters, enhancing light–matter interaction. This coupling scheme allows the demonstration of mutual excitation between two quantum dots separated in space by > 17 wavelengths. Our approach holds promise for achieving long-distance interaction without compromising interaction efficiency, which is essential for scaling up on-chip integration of quantum networks based on solid-state quantum emitters.