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This contribution reports the metal organic vapor phase epitaxy of InAsP/InP(001) quantum dots with a voluntary V-alloying obtained owing to an additional phosphine flux during InAs quantum dot growth. The quantum dots were studied by photoluminescence and transmission electron microscopy. We show that the additional phosphine flux allows to tune quantum dot emission around 1.55 μm while improving their optical properties. The comparison of the optical and structural properties of the InAsP quantum dots allows to deduce their phosphorus composition, ranging from 0% to 30% when the phosphine/arsine flow ratio is varying between 0 and 50. On the basis of the compositions deduced, we discuss on the effects of the phosphine flow and of the alloying on the quantum dot growth, structural, and optical properties. [ABSTRACT FROM AUTHOR]

This work reports on the influence of the InP cap-layer growth rate on the structural and optical properties of InAs/InP quantum dots (QDs) grown by metal-organic vapor phase epitaxy. A careful correlation between the structural and optical properties of the QDs completed by a modeling of their interband transition energy evidences the presence of different QD families with heights varying by monolayer steps. The analysis of transmission electron microscopy images and photoluminescence spectra demonstrates a drastic decrease of the QD height during the growth of the InP cap layer, due to As/P exchange. The efficiency of this erosion mechanism is shown to be strongly related to the QD exposure time to PH3, depending on the growth rate of the InP cap layer. [ABSTRACT FROM AUTHOR]

We investigate the structural and electronic properties of cleaved InAsP quantum dots grown by metal organic chemical vapor deposition on a (001) InP substrate by means of cross-sectional scanning tunneling microscopy and spectroscopy. We performed spatially and energetically resolved differential conductance measurements on several dots and thus mapped their electronic wave functions. Five distinct quantum dot energy levels are identified, all of them strongly confined inside the quantum dot. We further discuss the structural characteristics inferred from topographical images in the specific case of parallelogram-based InAsP/InP(001) quantum dots as a mean of investigating the size of a buried quantum dot. [ABSTRACT FROM AUTHOR]

By using superconducting single photon detectors, we perform time-resolved characterization of a small ensemble of InAsP/InP quantum dots grown by metal organic vapor phase epitaxy, emitting at wavelengths between 1.6 and 2.2 μm. We demonstrate that alloying phosphorus with InAs allows to shift the emission wavelength toward higher wavelengths, while keeping the high optical quality of these quantum dots at room temperature, with no decrease in their radiative lifetime. [ABSTRACT FROM AUTHOR]

The dynamic response of InAsP quantum dots, grown on InP(001) substrates by low-pressure metalorganic vapor phase epitaxy emitting around 1.55 μm, is investigated by means of time-resolved microphotoluminescence as a function of temperature. Exciton lifetime steadily increases from 1 ns at low temperature to reach 4 ns at 300 K while the integrated photoluminescence intensity decreases only by a factor of 23. These characteristics give evidence that such InAsP/InP quantum dots provide a strong carrier confinement even at room temperature and that their dynamic response is not affected by thermally activated nonradiative recombination up to room temperature. [ABSTRACT FROM AUTHOR]

This letter studies and differentiates the influence of both InAs growth rate and cap-layer growth rate on the density of capped InAs/InP(001) quantum dots (QDs) grown by metal-organic vapor phase epitaxy. The study shows that a decrease of the cap-layer growth rate leads to a reduction of the QD density. This reduction of QD density is of the same order as the kinetic reduction of QD density when decreasing InAs growth rate. Decreasing both InAs and cap-layer growth rates allows one to obtain a low density (9×107/cm2) of QD emitting at around 1.55 μm. [ABSTRACT FROM AUTHOR]

This letter reports on the growth mechanism of the InP cap layer over InAs/InP quantum dots (QDs) fabricated by metal organic vapor phase epitaxy (MOVPE). QD edges are shown to act as preferential nucleation sites for the InP cap layer, leading to the formation of InP domains around the nanostructures. As/P exchange reactions are at the origin of the planarization of the top of the QDs under P-rich ambient, thus leading to a final QD height equal to the local thickness of the InP cap layer. The possibility to use As/P exchange reactions to homogenize the height distribution of MOVPE grown InAs/InP QDs is discussed on the basis of these observations. [ABSTRACT FROM AUTHOR]

We report on the fabrication by low-pressure metalorganic vapor phase epitaxy of InAs/InP(001) quantum dots (QDs) emitting around 1.5 μm, and on the observation of microphotoluminescence (μPL) from a single QD in this wavelength range. The QDs are diamond shaped, with a density of 6.3·109 cm-2. μPL experiments were carried out on a QD sample covered with a gold mask containing apertures (diameter of 200 nm). Well defined peaks corresponding to the emission of single QDs were recorded between 1.24 and 1.6 μm. The analysis of the pump power dependence of their intensity allows us to discriminate between exciton and biexciton emission lines. [ABSTRACT FROM AUTHOR]

We report here on the structural and optical properties of selectively grown InAs/InP quantum dots. Our approach combines electron-beam lithography, reactive ion etching, and selective low-pressure metalorganic vapor phase epitaxy, which allows the growth of nanometer-scale InAs quantum dots directly on InP substrate and an improved control of their size uniformity and density. These nanogrown InAs dots exhibit a high-efficiency photoluminescence band pointed at 1.55 μm at room temperature. [ABSTRACT FROM AUTHOR]

In this letter, we report on the structural and optical properties of self-assembled InAs quantum dots (QDs) directly grown on InP(001) by low-pressure metalorganic vapor-phase epitaxy. Transmission electron microscopy reveals defect-free diamond-shaped QDs with a density as high as 2.5×1010 cm-2. The QD photoluminescence exhibits an intense peak centered around 1.58 μm (785 meV) at room temperature. Changing the growth rate allows one to control the QD density, while maintaining an intense emission centered at this wavelength. These promising results open the way for the realization of efficient InAs/InP(001) QD-based devices, such as lasers or single-photon sources. [ABSTRACT FROM AUTHOR]

The optical properties of single InAs1-xPx/InP quantum dots are investigated by spectrally resolved and time-resolved photoluminescence measurements as a function of excitation power. In the short-wavelength region (below 1.45 µm), the spectra display sharp distinct peaks resulting from the discrete electron-hole states in the dots, while in the long-wavelength range (above 1.45 µm), these sharp peaks lie on a broad spectral background. In both regions, cascade emission observed by time-resolved photoluminescence confirms that the quantum dots possess discrete exciton and multiexciton states. Single photon emission is reported for the dots emitting at 1.3 µm through antibunching measurements. [ABSTRACT FROM AUTHOR]

Abstract: This study describes the origin of the size and shape anisotropy of InAs/InP(001) quantum dots (QDs) grown by metalorganic vapor phase epitaxy (MOVPE). The geometry of the QDs is determined by carefully analyzing transmission electron microscopy (TEM) images. An analytical model adapted to our QD geometry is used to understand the formation mechanism of the QDs, and to describe the origin of their size dispersion. A shape transition from QDs to elongated quantum sticks (QS) is observed under As-poor growth conditions. This transition, driven by thermodynamics, is clearly described by our model. [Copyright &y& Elsevier]

Abstract: We present atomic-scale characterization of site-controlled InAs/InP(001) quantum dots grown by metal-organic chemical vapor deposition using nano-area selective area growth. We have developed for this purpose a process combining e-beam lithography, inductively coupled-plasma etching and focused ion beam etching to isolate a few quantum dots. The size, the shape and the composition of the quantum dots are investigated by Scanning Transmission Electron Microscopy. A comparison with the well-known single self-assembled quantum dots highlights the specificities of our growth mode compared to the Stranski–Krastanov growth mode. [Copyright &y& Elsevier]

Abstract: We demonstrate the feasibility of a new approach based on the nano selective area growth (nano-SAG), which allows the precise spacial localization, in the nanometer scale, of InAs/InP quantum dots (QDs) grown by low-pressure metal organic vapor-phase epitaxy. By using the hydrogen silsesquioxane-negative resist, we partially pattern the substrate in only one step (e-beam lithography) with dielectric masks containing nano-openings. We demonstrate that the one-step nano-SAG technique leads to the formation of site-controlled InAs/InP QDs with good structural properties, and allows the good control of the growth rate and thus of the QD size into the nano-openings. [Copyright &y& Elsevier]