Ordered gallium arsenide (GaAs) nanowires are grown by molecular-beam epitaxy on GaAs (111)B substrates using Au-catalyzed vapor–liquid–solid growth defined by nanochannel alumina (NCA) templates. Field-emission scanning electron microscope images show highly ordered nanowires with a growth direction perpendicular to the substrate. The size (i.e., diameter) distribution of the wires is drastically narrowed by depositing the gold catalyst through an NCA template mask; this narrows the size distribution of the gold dots and arranges them in a well-ordered array, as defined by the NCA template. The nanowire diameter distribution full width at half maximum on the masked substrate is 5.1 nm, compared with 15.7 nm on an unmasked substrate.

GaAs nanowires were grown on GaAs (100) substrates by vapor–liquid–solid growth. About 8% of these nanowires grew in 〈110〉 directions with straight, Y-branched or L-shaped morphologies. The role of strain-induced reduction in surface free energy is discussed as a possible factor contributing to the evolution of 〈110〉 nanowires. Kinking and branching is attributed to growth instabilities resulting from equivalent surface free energies for 〈110〉 growth directions. Transmission electron microscopy verified that 〈110〉 nanowires are defect free.

Highly ordered arrays of nanosized GaAs-based dots were successfully prepared on GaAs (001) substrates by molecular-beam epitaxy using selected area growth. Selected area growth employed alumina nanochannel array (NCA) templates formed by anodic oxidation, bonded to the GaAs substrates. Homogeneous GaAs dots, as well as compositionally modulated heterostructures within the nanosized dots, were demonstrated. In the latter case, multilayer InGaAs/GaAs heterostructured nanodot arrays were fabricated. Dot growth occurred only as defined by the template mask, resulting in a hexagonal lattice of dots with 100 nm period spacing, with dots retaining the circular lateral shape of the pores as determined by the NCA template pore size; dot diameters were adjustable from 45 to 85 nm for a lattice period of 100 nm. Cathodoluminescence spectra from an InGaAs/GaAs 10×10 dot array clearly showed an emission peak at 920 nm (5 K), confirming the formation of a high-quality InGaAs/GaAs quantum dot array.

Highly-ordered GaAs/AlGaAs quantum-dot arrays (QDA) were grown by molecular-beam epitaxy on GaAs (001) using masks of anodic nanochannel alumina (NCA). The QDA replicated the hexagonal lattice pattern of the NCA masks with period spacing of 100 nm. The circular disk-like dots were defined by the nanohole channels of NCA masks with size adjustable between 45 and 85 nm. Both single- and double-well GaAs/AlGaAs QDA exhibited strong photoluminescence. The single-well QDA showed a narrow peak at 1.64 eV with full width at half maximum of only 16 meV, indicating good size uniformity and crystal quality for the QDA. NCA masked epitaxial growth is thus shown to be a promising general approach for fabricating various heterostructure QDA, including both strained and lattice-matched heterostructures.

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We present optical spectra from numerous, single, self-assembled InAs/InP quantum dots. More than 50 individual dots are studied that emit in the 1.1-1.6 µm wavelength range. The dots are of high optical quality as judged by the clean, single exciton emission line at low power, the resolution limited linewidth, and the brightness. Each dot exhibits similar trends in the power evolution spectra, despite large variations in height and diameter. The level splittings in the p-shell increase with decreasing height, which we interpret to be from dot elongation along the [011] direction. The evolution of the spectra with increasing power agrees well with predictions from effective bond orbital calculations.1 Introduction Self-assembled semiconductor quantum dots have been studied extensively because of one's ability to tailor atom-like properties within a solid state medium. Such dots allow one to manipulate its properties via electric, magnetic, and vacuum fields and to perform experiments that demonstrate indistinguishable single photons [1], entangled photon pairs [2] and electro-optical spin storage [3]. To date, the vast majority of studies have utilized InAs/GaAs quantum dots emitting at wavelengths below 1 µm; primarily because of their high optical quality and because of the availability of both optical sources and highly efficient detectors within this wavelength range. Although InAs/GaAs dots have been used to demonstrate longer wavelength emission, a more promising candidate for wavelengths around 1.55 µm, where one finds the attenuation minimum for optical fibre, is the InAs/InP quantum dot system. At the present time, optical studies of single InAs/InP dots have not been as comprehensive as those for InAs/GaAs dots, although reports have addressed the challenges of both wavelength tuning and site selection [4][5][6][7][8]. Of the techniques available for site selection, some may result in exciton linewidth broadening and/or a reduction in signal to noise ratio; making it difficult to extract key intrinsic information such as fine structure, exchange interaction energies, binding energies and excited state structure etc. In addition, directed templating techniques [9] may alter the quantum dot properties as a result of the proximity to free surfaces or the presence of anisotropic piezoelectric potentials. With this in mind, it is necessary to produce a baseline for untemplated, naturally formed Stranski-Krastanow planar dots, from which site-selected dots can be compared. In the work presented here, we study in excess of 50 individual, planar InAs/InP quantum dots, with the aim of establishing the baseline behaviour discussed above. Dots are selected for their high optical quality, as inferred from their brightness and resolution limited linewidth. We compare the observed spectra to previously reported effective bond orbital model calculations [9].