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Holes in germanium nanowires have emerged as a realistic platform for quantum computing based on spin qubit logic. On top of the large spin–orbit coupling that allows fast qubit operation, nanowire geometry and orientation can be tuned to cancel out charge noise and hyperfine interaction. Here, we demonstrate a scalable approach to synthesize and organize Ge nanowires on silicon (100)-oriented substrates. Germanium nanowire networks are obtained by selectively growing on nanopatterned slits in a metalorganic vapor phase epitaxy system. Low-temperature electronic transport measurements are performed on nanowire Hall bar devices revealing high hole doping of ∼10(18) cm(–3) and mean free path of ∼10 nm. Quantum diffusive transport phenomena, universal conductance fluctuations, and weak antilocalization are revealed through magneto transport measurements yielding a coherence and a spin–orbit length of the order of 100 and 10 nm, respectively., Nano Letters, 22 (10), ISSN:1530-6984, ISSN:1530-6992

We demonstrate high-resolution cryogenic photoluminescence measurements on exciton complexes emitting ≈ 1 µm of a single-site-controlled highly-symmetric quantum dot-nanocavity system. Observed fine spectral features uncover the C3 v QD symmetry and cavity quantum electrodynamics.

Precise positioning of single quantum dots (QDs) in photonics crystal (PhC) cavities with nanometer-scale accuracy offers great promise for on-chip integrated quantum photonic circuit. In such coupled QD-cavity system, the decoherence fundamentally affects the coherent control for quantum communication and information processing. However, accessing to the strong-coupling regime and the impact of pure dephasing in such system have been rarely reported yet. Here, relying on our unique site-controlled pyramidal InGaAs/GaAs QDs – high-Q-PhC cavities platform, we investigate the cavity quantum electrodynamics towards strong-coupling regime mediated by pure dephasing. We demonstrate the anti-crossing and mutual linewidth narrowing of the single excitonic emission strongly coupled to cavity mode near resonance. We further present the signatures of Rabi-like oscillation and quantum beating between upper and lower branch of polariton.

We demonstrate the controllable exciton-cavity mode interaction mediated by pure dephasing in a single site-controlled quantum dot-nanocavity system. With varying detuning, Purcell enhanced dynamics and phonon-assisted cavity feeding sequentially dominate the exciton-cavity mode interaction.

A system of two site-controlled semiconductor quantum dots (QDs) is deterministically integrated with a photonic crystal membrane nano-cavity. The two QDs are identified via their reproducible emission spectral features, and their coupling to the fundamental cavity mode is established by emission co-polarization and cavity feeding features. A theoretical model accounting for phonon interaction and pure dephasing reproduces the observed results and permits extraction of the light-matter coupling constant for this system. The demonstrated approach offers a platform for scaling up the integration of QD systems and nano-photonic elements for integrated quantum photonics applications.

Growth of InGaAs/GaAs quantum dots (QDs) in inverted pyramids on pre-patterned {111}B GaAs substrates is a versatile technique allowing for precise site and emission energy control. We report on the fabrication of QDs with a wavelength setting within a range of ~100 meV achieved in a single growth step by varying the pyramid size and without compromising the optical quality. Low-temperature micro-photoluminescence spectra of the QD ensembles exhibit low inhomogeneous broadening (~15 meV) and excitonic linewidths as low as 50 μeV. Moreover, we demonstrate the selective energy tuning of a single QD embedded within an ensemble of QDs spectrally blue-shifted by as much as 40 meV, which is of interest for single QD spectroscopy and the fabrication of integrated multi-wavelength single photon sources.

Partial suppression of the spectral diffusion of quantum dot (QD) excitons tuned to resonance of a nano-photonic cavity is reported. The suppression is caused by the Purcell enhancement of the QD-exciton recombination rate, which alters the rate of charging of the solid-state environment by the QD itself. The effect can be used to spectrally-stabilize solid-state emitters of single photons and other non-classical states of light.

We investigate a photonic crystal structure where distant, identical nanocavities incorporating site-controlled semiconductor quantum dots are coupled with a bus waveguide. We show that the cavities can be resonant frequency matched even upon fabrication imperfection.

We describe the fabrication, epitaxial growth and photoluminescence (PL) spectra of systems of site-controlled pyramidal quantum dots (QDs) integrated with photonic crystal (PhC) membrane cavities. The spectra of the individual QDs are characterized by scanning micro-PL spectroscopy, and the cavity modes are identified by polarization-resolved PL measurements and modeling. Weak coupling of systems incorporating up to four identifiable QDs with single modes of the PhC cavities is demonstrated. (C) 2014 Elsevier B.V. All rights reserved.

The progress of 1.3- and 1.5-μm waveband wafer-fused VCSELs is reported. The emission of single mode power of 6 - 8 mW at room temperature and up to 3 mW at 80°C were demonstrated. 10-Gb/s full wavelength-set VCSEL devices for CWDM systems with high yield and Telcordia-reliability were industrially manufactured. By increasing the compressive strain in the QWs and reducing the cavity photon life time the modulation bandwidth was increased to 11.5 GHz, and large-signal data transmission experiments show error-free operation and open eye diagrams from 25 to 35 Gb/s in both B2B and after 10-km, respectively.

Long wavelength (LW) vertical cavity surface emitting lasers (VCSELs) are important low cost and low power consumption sources for optical interconnects in data centers, sensing and spectroscopy [1,2]. We discuss here the recent progress in the design, fabrication and industrialization of such devices made by using wafer fusion, which allows integration of GaAs-based distributed Bragg reflectors (DBRs) with InP-based active structures and an independent optimization of the mirror and active cavity properties before the fusion. Both the GaAs-based mirrors and InP-based optical gain structures are grown by metalorganic vapor phase epitaxy (MOVPE). The VCSEL structure comprises an InP-based active region with 5 to 6 InAlGaAs compressively strained quantum wells (QWs) as the gain medium and tunnel junction (TJ) aperture for current and optical confinement, double-fused to two GaAs/AlGaAs-based Bragg mirrors (Fig.1a). By epitaxial growth, device design and processing optimization 1.3- and 1.5μm waveband VCSELs emitting single mode power of 6–8-mW at room temperature and up to 3-mW at 80°C were demonstrated (Fig.1b) [3,4]. Moreover, industrially manufactured 10-Gb/s full CWDM wavelength-set VCSEL devices for coarse wavelength division multiplexing systems with high yield and Telcordia-reliability have been developed [5–6].

We investigate the optical coupling of excitons confined in site-controlled semiconductor quantum dots (QDs) with the modes of photonic crystal (PhC) cavities membrane cavities and waveguides. The structures are fabricated by organometallic vapor phase epitaxy of InGaAs/GaAs heterostructures on patterned (111)B GaAs substrates combined with electron-beam-based nanolithography. We elucidate the role of pure dephasing and phonon interaction on the weak exciton-cavity mode coupling, and demonstrate the simultaneous coupling of several QDs to the same optical mode of various PhC cavity configurations. In addition, coupling of QD systems to PhC waveguides for implementing single photon transport in the face of optical disorder is studied. Implications on the potential of constructing integrated quantum photonic circuits for on-chip manipulation of quantum light will be discussed.

Using site-controlled semiconductor quantum dots (QDs) free of multiexcitonic continuum states, integrated with photonic crystal membrane cavities, we clarify the effects of pure dephasing and phonon scattering on exciton-cavity coupling in the weak-coupling regime. In particular, the observed QD-cavity copolarization and cavity mode feeding versus QD-cavity detuning are explained quantitatively by a model of a two-level system embedded in a solid-state environment.

We demonstrate the fabrication of arrayed, site-controlled pyramidal InGaAs/GaAs quantum dots (QDs) grown by metalorganic vapor phase epitaxy with tailored emission energy and periods as small as 200 nm, suitable for the integration with compact photonic structures. The observed variation of the QD emission energy with the geometric parameters of the array is attributed to adatom and precursor diffusion mechanisms during epitaxial growth. By adjusting the pattern geometry, the emission energy can be tuned over a wide range of ∼80 meV around 1.4 eV, with inhomogeneous broadening

Keywords: electronic structure ; epitaxy ; nanostructures ; photoluminescence ; quantum dots ; Confinement ; Computation ; Gates ; Wires Reference LPN-ARTICLE-2009-008doi:10.1002/smll.200801214View record in Web of Science Record created on 2009-07-31, modified on 2017-05-12

A sequence of photoluminescence spectroscopy based methods are used to rigorously identify and study all the main spectral features (more than thirty emission lines) of site controlled InGaAs/AlGaAs quantum dots (QDs) grown along [111]B in inverted tetrahedral pyramids. The studied QDs reveal signatures of one confined electron level, one heavy-hole-like level and one light-hole-like level. The various heavy-light-hole hybrid exciton complexes formed in these QDs are studied by polarization resolved spectroscopy, excitation power dependence, crystal temperature dependence and temporal single photon correlation measurements. The presented approach, which only requires a minimal theoretical input, enables strict spectral identification of the fine structure patterns including weak and spectrally overlapping emission lines. Furthermore, it allows the involved electron-hole and hole-hole exchange interaction energies to be deduced from measurements. Intricate fine structure patterns are qualitatively understood by group theory and shown to be very sensitive to the exact symmetry of the QD. Emission patterns influenced by hole-hole exchange interactions are found to be particularly useful for identifying QDs with high $C_{3v}$ symmetry and for probing symmetry breaking., Comment: 20 pages, 22 figures

MOVPE epitaxial growth and design optimisation of 1.5 μm vertical cavity surface emitting lasers (VCSELs) for high power, single mode and high-temperature operation are presented. The VCSEL structure comprises a strain-compensated InAlGaAs MQW active region, a p ++ /n ++ In(Al)GaAs tunnel junction and top and bottom AlGaAs/GaAs fused distributed Bragg reflectors. All epitaxial layers were grown by low-pressure MOVPE in nitrogen atmosphere. Excellent optical and electrical confinement is obtained by wafer-bonding of the top mirror on tunnel junction pre-etched mesas. Devices with 7 μm aperture show single transverse mode CW operation up to 4 mW at room temperature, with 30–35 dB side-mode suppression ratio and a far field divergence angle of 9°. At 85 °C, a record single mode high emission power up to 1.7 mW is demonstrated.

Low-temperature photoluminescence (PL) was used to optimize the structural and optical quality of 2–15 nm thick GaAs/AlGaAs quantum wells (QWs). GaAs wafers, misoriented off (1 0 0) towards 〈1 1 1〉A and 〈1 1 1〉B were used, covering the 0–0.6° misorientation range in steps of 0.1°. A dramatic reduction in the 10 K PL linewidth is observed for all 0.2–0.3° misorientations, as compared to nominally oriented wafers: on 2, 5 and 15 nm thick QWs, linewidths fall from 23, 8 and 3 meV to 6, 3 and 2.5 meV, respectively, among the narrowest reported to date for similar structures. Above 0.3° misorientation, the emission broadens to become, at 0.6°, comparable or worse than for the exact (1 0 0) samples. The 4 K electron mobility of two-dimensional electron gases grown on similar, misoriented substrates increases steadily and then decreases again at larger misorientations.

Reference LPN-ARTICLE-2002-006doi:10.1016/S1386-9477(02)00225-4View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

We fabricated and studied a system comprising four site-controlled semiconductor quantum dots (QDs) embedded in a linear photonic crystal membrane cavity. The excellent position control and small spectral broadening permit coupling of the emission of all four QDs to the same photonic cavity modes. This is corroborated by co-polarization of the QD and cavity emission lines, as well as reduction in decay time, both with characteristic dependence on QD-cavity energy detuning. Scaling up to larger QD systems is discussed.

We have combined atomic force microscopy (AFM) and 2D+1 Monte-Carlo simulations to investigate the formation of local potential minima in self-ordered AlGaAs/GaAs V-groove quantum wires. In order to determine the origin of these potential fluctuations along the wire axis in the sub-micrometer range, we studied by AFM the morphology of V-grooved substrates at different stages of processing and growth. Monte-Carlo simulations are used to study the influence of the growth kinetics on the self-limiting profile in disordered V grooves. Our model evidences a re-entrant mechanism in which the sidewalls roughness induces monolayers thickness fluctuations along the wire axis. The influence of the growth conditions on the quantum wire disorder is discussed.

Cross-sectional Atomic Force Microscopy (AFM) measurements in air combined with finite element (FE) calculations are used to study the (110) cleaved surface of compressive InGaAs/GaAs quantum wells (QWs) and V-groove quantum wires (QWRs). The elastic relaxation is clearly identified as the main cause of the AFM height contrast revealed on the cleaved edge. In particular, we show that the native oxidation due to the air exposure does not alter significantly the elastic deformation of the cleaved surface. This simple technique, which does not require any sample preparation or chemical etching, is applied to the characterization of the growth front evolution during the organometallic chemical vapor deposition growth on V-grooved substrates. Making use of the AFM surface profile measurements evidences the segregation of indium in the InGaAs film.

We present direct evidence of stimulated emission from the one-dimensional ground subband in optically pumped GaAs/AlGaAs V-groove quantum wire structures. We find that the lasing is sustained by excitonic gain. Spectra detected for low excitation power and above the lasing threshold demonstrate that lasing originates from localized excitons.

Reference LPN-ARTICLE-2000-006doi:10.1002/1521-396X(200003)178:1 3.0.CO;2-5View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

We report the fabrication and the optical properties of dense arrays of strained InGaAs/GaAs V-groove quantum wires (QWRs) embedded in wavelength size planar Bragg microcavities, made using a two-step organometallic chemical vapor deposition (OMCVD). Growth front evolution and top surface morphology of GaAs on the corrugated substrate were investigated as a function of the growth temperature (550–625°C) and the pitch of the V-groove grating (3–0.25 μm). Based on these studies, a growth temperature of 550°C and a grating pitch of 0.25 μm were selected to achieve sizes compatible with simultaneous quantum confinement for electron (≈10 nm wide wires) and photon (≈0.25 μm thick cavities) states. Reference arrays of uniform, nanometer-size, crescent-shaped, InGaAs QWRs with densities up to 4QWRs/μm were realized, exhibiting a narrow (8 meV) and intense emission from one-dimensional excitonic states at low temperature. Similar QWRs were then successfully embedded in planar microcavities, showing brighter (×50) emission with a strongly reduced linewidth (1 meV) due to resonant coupling between the wire emission and the microcavity modes.

The growth the GaAs/GaAlAs quantum wires by organometallic chemical vapor deposition on V-grooved substrates relies on the formation of a self-limiting AlGaAs surface profile and the thickness modulation in the form of a crescent of the GaAs layer. In order to gain understanding on the growth process at the atomic level, we developed a two-dimensional Monte-Carlo simulation based on the solid-on-solid model. In good agreement with experimental results, our kinetic model shows that the self-limited profile results from the competition between the growth rate anisotropy on the different facets of the groove and the surface diffusion of adatoms. The predictions of the growth modeling are experimentally employed to control at the nanometer scale the shape of quantum wires using successive changes in the growth conditions. This understanding of the growth mechanisms opens the way to an accurate control of the quantum confinement in quantum wires.

We demonstrate 2-mum wavelength, wafer-fused In(Al)GaAs-InP-AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting single-mode power of 0.5 mW at room temperature with a threshold current of 4 mA and sidemode suppression ratio of over 30 dB. These devices can be continuously tuned with current by 5 nm without mode hopping, with a tuning rate of 0.31 nm/mA. These features demonstrate the potential of these long wavelength VCSELs for gas sensing and other optical spectroscopy applications.

We have studied the capabilities of chemical beam epitaxy (CBE) to produce high-gain media for long-wavelength (1.5 mu m) vertical cavity surface emitting lasers (VCSELs). Using a parameter pair of low growth temperature and small V/III ratio the integration of up to 15 highly strained (1.78%) InAsP quantum wells (QWs) into a periodic gain structure (PGS) is successfully demonstrated. In this work we present data of atomic force microscopy (AFM), X-ray diffraction, reflectivity and electro-luminescence measurements that prove the very good structural and optical quality of this CBE grown PGS. As an alternative to conventional multi quantum well(MQW) systems as active layers, a high-performance PGS may be used in a VCSEL structure to reduce the very strict requirements on the InP-based distributed Bragg reflectors (DBRs) or to increase the achievable output power. Due to the use of thickness-reduced InP-based DBRs in conjunction with a PGS as the active region the fabrication of fully epitaxial grown long-wavelength VCSELs might also be possible with CBE. (C) 1998 Elsevier Science B.V. All rights reserved.

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/InGaAsP and InGaAs/InGaAsP laser diodes on GaAs substrates have been obtained by localized wafer fusion at 650 degrees C.

This article reports on the fabrication and characterization of wafer fused heterojunctions between p-InP and p-GaAs. Secondary ion mass spectroscopy was used to characterize doping profiles across the interface as well as the interface contamination with oxygen or carbon. The crystalline quality of the fused material was characterized using cross section and plan-view transmission electron microscopy. The electrical properties of the fused interface were studied as a function of various doping elements such as Be and Zn in InP or Zn and C in GaAs as well as for different acceptor concentrations in GaAs. Finally, the electrical characteristics were analyzed using a numerical model that includes thermionic emission and tunneling across the heterobarrier.

The development of the 10GBASE-LX4 communication standard for aggregated 10-Gb/s rates feeds the need for low-cost laser sources in the 1275-1350-nm wavelength range operating at modulation rates of 3.125 Gb/s. We present comprehensive characterization of wafer fused vertical-cavity surface-emitting lasers with characteristics that meet the IEEE802.3ae specification for 10GBASE-LX4. These include output power greater than 1.5 mW up to 80degC, wavelength around 1340 nm, single-mode emission and modulation at 3.125 Gb/s, and wide open eyes with rise and fall times below 100 ps up to 70degC

Reference LPN-ARTICLE-1997-009doi:10.1016/S0022-0248(96)00955-4View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12

High-performance vertical-cavity surface-emitting lasers (VCSELs) emitting in the 1310-nm waveband are fabricated by bonding AlGaAs-GaAs distributed Bragg reflectors on both sides of a InP-based cavity. A 2-in wafer bonding process is optimized to produce very good on-wafer device parameter uniformity. Carrier injection is implemented via double intracavity contact layers and a tunnel junction. A 1.2-mW single-mode output power is obtained in the temperature range of 20/spl deg/C-80/spl deg/C. Modulation capability at 3.2 Gb/s is demonstrated up to 70/spl deg/C. Overall VCSEL performance complies with the requirements of the 10 GBASE-LX4 IEEE.802.3ae standard, which opens the way for novel applications of VCSELs emitting in the 1310-nm band.

The properties of InGaAsN V-groove QWRs are assessed here by polarization-dependent photoluminescence (PL) and micro-magneto-PL. Both the polarization anisotropy of the QWR emission and the strong dependence of the diamagnetic shift on the orientation of the applied magnetic field confirm the 1D nature of the QWR excitons. Further, the possibility of passivating N impurities by H irradiation is used to estimate the N content (x) in the QWRs by turning off the effects of N incorporation. Both the H-induced blueshift of the QWR emission (70 meV) and the measured value of the electron effective mass are consistent with x similar to 1%. Nitrogen is also found to enhance the In intake in the QWR, likely due to the strain reduction resulting from the smaller lattice parameter of the InGaAsN alloy. Such strain reduction is also responsible for the quick decay of the degree of linear polarization (rho) of the QWR emission with increasing temperature, indicating a small splitting between the QWR valence-band levels. In fully hydrogenated samples, conversely, rho remains roughly constant up to similar to 240 K, suggesting the recovery of a larger energy separation between the QWR hole states upon N passivation. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A p + -In 0.56 Ga 0.44 As/n-In 0.56 Ga 0.44 As/n-InP/n + -InP heterostructure has been realized by chemical beam epitaxy and characterized using cathodoluminescence (CL) and electron beam-induced current (EBIC) techniques. These techniques allowed the visualization, location and density measurement of a misfit dislocation network due to the compressive strain between the epitaxial layers. The structure was found to be partly relaxed with the dislocation network located in the InP buffer under the hetero-interface and with a dislocation density between 1.9 × 10 7 and 5.3 × 10 7 cm −2 according to the area chosen; no threading dislocations were found in the InGaAs layer, which demonstrates the efficient role of the buffer as a dislocation barrier. Moreover, some important diffusion-recombination (DR) parameters, such as the minority carrier diffusion length, and the surface and interface recombination velocities, have been evaluated throughout the whole structure by fitting a CL theoretical model to experimental measurements. Photon recycling in the highly doped substrate has been evidenced by spectroscopic and semiquantitative measurements.

When InP is grown by chemical beam epitaxy on substrates patterned with ridges oriented along [110] with (111)B sidewall planes, the migration of In species on the surface changes direction with growth temperature. The movement is from the ridge to the valley through the sidewall above 505 degrees C, and from the sidewall to the ridge below 495 degrees C. By using this specific growth behavior, we have obtained a triangular prism-shaped buried heterostructure with a narrow active region. We also present an estimation of the growth temperature dependence of the diffusion length on each plane and propose a model explaining the above migrations.

Growth temperatures between 450 and 520 degrees C and V/III ratios of 2-8 were explored to optimize the crystalline quality and the transport properties of compressively strained InxGa1-xAs/InP heterostructures (0.53 < x < 1). 77 K Hall mobilities as high as 118000 cm(2) V-1 s(-1) with n(s) = 1.4 x 10(12) cm(-2) were measured on structures incorporating an In0.8Ga0.2As channel grown with optimized conditions.

We demonstrate widely tunable InAlGaAs-InP-AlGaAs-GaAs optically pumped vertical-cavity surface-emitting lasers operating in the 1.55-/spl mu/m waveband. The tuning range of 32 nm is achieved by applying a low tuning voltage of 4 V. Maximum single-mode output power of 2 mW with less than 1.5-dB power variation over the whole tuning range and side-mode suppression ratio in excess of 30 dB have been obtained.

We demonstrate 1.5-/spl mu/m waveband wafer-fused InGaAlAs-InP-AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting high single-mode power of 1.5 mW at room temperature with sidemode suppression ratio of over 30 dB and a full-width at half-maximum far field angle of 9/spl deg/. These devices have thermal resistance value below 1.5 K/mW and are emitting 0.2 mW at 70/spl deg/C. VCSELs with a wavelength span of 40-nm emission are produced from the same active cavity material, which shows the potential of realizing multiple-wavelength VCSEL arrays.

When a growth interruption is applied to the top interface of a nominally 3 monolayers (ML) thick InAs quantum well (QW), grown on an InP substrate, the InAs layer relaxes by formation of three-dimensional (3D) islands. The emission from the QW is split into at least 8 peaks. Each peak corresponds to an integral number of MLs of InAs. Using cathodoluminescence imaging and photoluminescence excitation spectroscopy, we demonstrate that the emission originates in 3D islands with a lateral extension of less than 1 mu m. Furthermore, most of the 3D islands are completely isolated, separated by InP, even though there are 3D islands of different thicknesses that are connected. A conclusion from our investigation is that the whole InAs layer, rather than just the top ML, is involved in the 3D island formation.

The dynamics of acoustic vibrations in terahertz quantum cascade laser structures (THz-QCLs) is studied by means of femtosecond pump-probe spectroscopy. The phonon modes are characterized by the folding of the acoustic dispersion into an effective reduced Brillouin zone. An accurate identification of this dispersion allows the sample structure and periodicity to be determined with high precision on the order of 0.1%. By temperature tuning the energy of the electronic levels of the system and performing wavelength dependent measurements, we are able to study the impulsive resonant generation and detection of coherent acoustic phonon modes. These results are supported by simulations of the electronic system that well explain the experimental observations. The effects of interface (IF) roughness on coherent acoustic phonon spectra are clearly observed for equal nominal THz-QCL structures but with different interface qualities. Fil: Bruchhausen, Axel Emerico. University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lloyd Hughes, James . University of Oxford; Reino Unido Fil: Hettich, Mike . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania Fil: Gebs, Raphael . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania Fil: Grossmann, Martin . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania Fil: Ristow, Oliver . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania Fil: Bartels, Albrecht . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania Fil: Fischer, Milan . Institute of Quantum Electronics; Suiza Fil: Beck, Mattias . Institute of Quantum Electronics; Suiza Fil: Scalari, Giacomo . Institute of Quantum Electronics; Suiza Fil: Faist, Jérôme . Institute of Quantum Electronics; Suiza Fil: Rudra, Alok . Ecole Polytechnique Federale de Lausanne; Suiza Fil: Gallo, Pascal . Ecole Polytechnique Federale de Lausanne; Suiza Fil: Kapon, Eli . Ecole Polytechnique Federale de Lausanne; Suiza Fil: Dekorsy, Thomas . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemania

We have measured the temperature dependence of the conductance of long V-groove quantum wires fabricated using GaAs/AlGaAs heterostructures, in a wide temperature range (200 mK < T < 4.2 K). We find that for our quantum wires the Fermi velocity can be as low as nu(F) congruent to 5 x 10(4) m/s, corresponding to an interaction parameter value of g congruent to 0.56. This value suggests that our data are consistent with theories developed within the framework of the Luttinger liquid model in the presence of a single strong barrier (weak link).

The properties of single site-controlled InGaAsN quantum wires (QWRs)-both untreated and irradiated with atomic hydrogen-are probed by micro-magnetophotoluminescence spectroscopy. The strong anisotropy of the diamagnetic shift measured for different orientations of the applied magnetic field confirms the one-dimensional nature of the QWR carrier wave function. In addition, the strain reduction associated with N incorporation is found to promote a larger indium intake in the QWR, enabling the realization of site-controlled QWRs emitting at long (>= 1.3 mu m), technologically relevant wavelengths.

We investigated the effects of hydrogen irradiation on the degree of linear polarization, rho, of the light emitted by site-controlled, dilute-nitride InGaAsN V-groove quantum wires (QWRs). While in the as-grown sample the polarization of the QWR emission is highly sensitive to the increasing temperature (T), after sample hydrogenation the value of rho remains nearly unchanged (and similar to 25%) for T

The reactive ion etching of the GaInP/GaAs multilayer structure using SiCl 4 , Cl 2 and Ar was examined. Different plasma compositions were tested and a mixture containing principally SiCl 4 was chosen. Experiments were performed with power densities between 0.01 and 0.78 W cm −2 and at pressures between 2 and 50 mTorr. Etching mechanisms and the surface morphology are discussed briefly and compared with results for substrate materials processed under the same plasma conditions. Orientation independent etching of 5 μm high posts with no selectivity between GaInP and GaAs is reported. The sidewalls are smooth and contamination free.

A thin InAs layer grown in a quasi-two-dimensional film over InP reorganizes into islands if left to anneal under arsine. This surface transformation is inhibited at lower arsine fluxes. With increasing temperature, the surface transformation is activated as long as the effective arsine coverage is sufficient.

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, making use of the high spectral uniformity of the QDs and designing PhC cavities with different hole radii. Efficient coupling of the PhC cavity modes both to the ground state and to the excited state transitions of the QDs was observed, whereas no evidence for far off-resonant coupling was found.