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We report a model for metalorganic vapor-phase epitaxy on non-planar substrates, specifically V-grooves and pyramidal recesses, which we apply to the growth of InGaAs nanostructures. This model—based on a set of coupled reaction-diffusion equations, one for each facet in the system—accounts for the facet-dependence of all kinetic processes (e.g., precursor decomposition, adatom diffusion, and adatom lifetimes) and has been previously applied to account for the temperature-, concentration-, and temporal-dependence of AlGaAs nanostructures on GaAs (111)B surfaces with V-grooves and pyramidal recesses. In the present study, the growth of In0.12Ga0.88As quantum wires at the bottom of V-grooves is used to determine a set of optimized kinetic parameters. Based on these parameters, we have modeled the growth of In0.25Ga0.75As nanostructures formed in pyramidal site-controlled quantum-dot systems, successfully producing a qualitative explanation for the temperature-dependence of their optical properties, which have been reported in previous studies. Finally, we present scanning electron and cross-sectional atomic force microscopy images which show previously unreported facetting at the bottom of the pyramidal recesses that allow quantum dot formation. [ABSTRACT FROM AUTHOR]

The influence of preoxidation GaAs surface treatment over the atomic force microscopy-induced local anodic oxidation (LAO) is investigated in this paper. By immerging the GaAs samples into NaOH aqueous solutions, higher nano-oxides with better height distribution could be observed after LAO. The phenomenon is attributed to the hydrophilic surfaces obtained after the treatment such that higher local humidity and uniform water molecular distribution would be obtained on the GaAs surfaces, by using the higher nano-oxides with better height uniformity, nanomesas by using wet chemical etching, and nanometal contact after oxide lift-off are fabricated. [ABSTRACT FROM AUTHOR]

This study explores the growth and effects of a ten-period InAs/GaAs quantum-dot infrared photodetector (QDIP). With a uniform quantum-dot (QD) size distribution and a QD density of 2.8×1010 cm-2, this 10 K photoluminescence spectrum shows a peak energy at 1.07 eV and a narrow full width at half maximum of 31.7 meV. The QDIP exhibits an asymmetric response under different voltage polarities and a high responsivity of 1.7 A/W at -1.1 V. Another noticeable observation in the spectral response of the device is the 6 μm peak detection wavelength with a high spectral broadening Δλ/λ of 0.67. By analyses of the photoluminescence excitation spectrum and the temperature dependence of spectral response, the wide spectral response of the QDIP is attributed to the summation of transitions between QD excited states and the wetting layer states, instead of transitions between QD ground state and higher excited states. [ABSTRACT FROM AUTHOR]

Ten-period InAs-GaAs quantum-dot (QD) infrared photodetectors grown under different In adatom supply procedures are investigated. Two In adatom supply procedures of In shutter 1) always opened and 2) periodically opened/closed are adopted in this letter. Larger QD sizes in both height and diameter and more uniform size distribution are observed for samples grown under an In shutter periodically opened/closed condition. The device with QDs grown under the In shutter always opened condition has revealed shorter detection wavelengths and enhanced normal incident absorption. The phenomenon shows that beside the increase of energy difference between confinement states, smaller QD sizes would also enhance the normal incident absorption predicted for the theoretically zero-dimensional QD structures. [ABSTRACT FROM PUBLISHER]

In this article, we report the growth of InAs/GaAs quantum dots (QDs) grown under different As4-supply procedures. The growth of the investigated samples carried out by the three procedures of As shutter always opened, As shutter initially opened, and As shutter initially closed. The samples grown by the former two approaches show a uniform QD distribution and the multiple-peak luminescence, which correspond to ground-state, first-excited-state, and second-excited-state luminescence, while that grown by the latter only shows large InAs islands. The results suggest that the As-stabilized condition at the initial stage of QD growth is very critical for the high-quality QD formation. [ABSTRACT FROM AUTHOR]

In this article, the authors investigate the influences of different InAs coverages on the photoluminescence excitation (PLE) spectra and spectral responses of InAs/GaAs quantum-dot infrared photodetectors (QDIPs). An increase in InAs coverage would lead to an increase in energy separation between heavy-hole state and light-hole state in the wetting layer (WL) region in the QD PLE spectra. The results suggest that most of the strain resulted from the InAs/GaAs lattice mismatch may be accumulated in the WL instead of the QD region. Also observed are the similar energy separations of energy levels responsible for the intraband absorption in the PLE spectra of the QDIPs such that similar detection wavelengths are observed for the devices. [ABSTRACT FROM AUTHOR]