Optical studies of GaInP/GaP quantum dots (original) (raw)
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Optimization of MOVPE-grown In x Ga 1− x P self-assembled quantum dots on GaP
Journal of Crystal Growth, 2002
We discuss the growth of In x Ga 1Àx P quantum dots on nominally (1 0 0)-oriented GaP substrates by low-pressure metal organic vapor phase epitaxy. Parameters like the growth temperature, thickness of the InGaP layer, strain, via the indium composition of In x Ga 1Àx P, and the post-growth ripening time have been varied to study their effect on the growth of self-assembled InGaP quantum dots in Stranski-Krastanow mode. Under optimized conditions quantum dots with lateral dimension B50 nm and height B5 nm and a density >10 10 cm 2 have been achieved. Surface photovoltage spectroscopy is shown to be a convenient and sensitive technique to monitor the various stages in the growth of quantum dot structures. r
Theoretical and experimental studies of (In,Ga)As/GaP quantum dots
Nanoscale Research Letters, 2012
In,Ga)As/GaP(001) quantum dots (QDs) are grown by molecular beam epitaxy and studied both theoretically and experimentally. The electronic band structure is simulated using a combination of k·p and tight-binding models. These calculations predict an indirect to direct crossover with the In content and the size of the QDs. The optical properties are then studied in a low-In-content range through photoluminescence and time-resolved photoluminescence experiments. It suggests the proximity of two optical transitions of indirect and direct types.
Electronic wave functions and optical transitions in (In,Ga)As/GaP quantum dots
Physical Review B, 2016
We study the complex electronic band structure of low In content InGaAs/GaP quantum dots. A supercell extended-basis tight-binding model is used to simulate the electronic and the optical properties of a pure GaAs/GaP quantum dot modeled at the atomic level. Transitions between hole states confined into the dots and several X Z-like electronic states confined by the strain field in the GaP barrier are found to play the main role on the optical properties. Especially, the calculated radiative lifetime for such indirect transitions is in good agreement with the photoluminescence decay time measured in time-resolved photoluminescence in the µs range. Photoluminescence experiments under hydrostatic pressure are also presented. The redshift of the photoluminescence spectrum with pressure is also in good agreement with the nature of the electronic confined states simulated with the tight-binding model.
Structural and electrooptical characteristics of quantum dots emitting at 1.3 μm on gallium arsenide
IEEE Journal of Quantum Electronics, 2001
We present a comprehensive study of the structural and emission properties of self-assembled InAs quantum dots emitting at 1.3 m. The dots are grown by molecular beam epitaxy on gallium arsenide substrates. Room-temperature emission at 1.3 m is obtained by embedding the dots in an InGaAs layer. Depending on the growth structure, dot densities of 1-6 10 10 cm 2 are obtained. High dot densities are associated with large inhomogeneous broadenings, while narrow photoluminescence (PL) linewidths are obtained in low-density samples. From time-resolved PL experiments, a long carrier lifetime of 1 8 ns is measured at room temperature, which confirms the excellent structural quality. A fast PL rise (rise = 10 2 ps) is observed at all temperatures, indicating the potential for high-speed modulation. High-efficiency light-emitting diodes (LEDs) based on these dots are demonstrated, with external quantum efficiency of 1% at room temperature. This corresponds to an estimated 13% radiative efficiency. Electroluminescence spectra under high injection allow us to determine the transition energies of excited states in the dots and bidimensional states in the adjacent InGaAs quantum well.
Structural and Optical Behavior of Germanium Quantum Dots
Chinese Physics Letters, 2012
Ge nanodots are grown on a Si(100) substrate by radio frequency magnetron sputtering deposition technique. The role of annealing temperature on structural and optical properties is studied. The formation of nanodots is confirmed by X-ray diffraction pattern and the particle size is estimated to be ~ 6.5 to 8.5 nm. The structure and optical characterizations are made using, Energy dispersive X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, photoluminescence and Raman spectroscopy. The interface intermixing and the size of the nanodots are determined from Raman spectra and field emission scanning electron micrograph. Root mean square roughness and number density are found to be strongly influenced by annealing temperature. Photoluminescence spectra shows the strong emission peak at 3.21 eV accompanied by two weaker peaks at around 2.85 and 4.13 eV in the visible region. The red shift of the strong peak ~ 0.05 eV is attributed to the effect of quantum confinement.
Nanotechnology, 2012
We demonstrate a method to controllably reduce the density of self-assembled InP quantum dots (QDs) by cyclic deposition with growth interruptions. Varying the number of cycles enabled a reduction of the QD density from 7.4 × 10 10 cm −2 to 1.8 × 10 9 cm −2 for the same total amount of deposited InP. Simultaneously, a systematic increase of the QD size could be observed. Emission characteristics of different-sized InP QDs were analyzed. Excitation power dependent and time-resolved measurements confirm a transition from type I to type II band alignment for large InP quantum dots. Photon autocorrelation measurements of type I QDs performed under pulsed excitation reveal pronounced antibunching (g (2) (τ = 0) = 0.06 ± 0.03) as expected for a single-photon emitter. The described growth routine has great promise for the exploitation of InP QDs as quantum emitters.
Short wavelength emission of AlGaInP quantum dots grown on GaP substrate
Nanotechnology, 2011
We report on growth of AlGaInP quantum dots (QDs) with Al-contents between 0% and 10% on GaP substrate by gas-source molecular beam epitaxy and the investigation of their morphological and low temperature photoluminescence properties. These high areal density QDs show short wavelength emission between 575 nm and 612 nm depending on their composition. The authors interpret the QD emission to originate from indirect type-II transitions. This interpretation is supported by a singleband effective mass model, which allows to describe the role of different barrier compositions on the QD emission. Time-resolved photoluminescence measurements are performed to verify the calculations.
Electronic, optical, and structural properties of (In,Ga)As/GaP quantum dots
Physical Review B, 2012
We have studied corrugated quantum wells as a semiconductor quantum wire structure. The quantum well corrugation results from a step bunching effect during epitaxial growth on vicinal ͑111͒ GaAs substrates and might be used to form a quantum wire superlattice. The strain and piezoelectric effects were studied both by an atomistic valence force field method and by an elastic continuum model. Within the elastic continuum model we also studied the electromechanical coupling. The electronic band structure was calculated with the eightband k•p model. The nonphysical oscillating solutions were eliminated by appropriate fine tuning of the material parameters. We have also studied the density of states and the polarization dependence of interband light absorption in the electric dipole approximation.
Room temperature photoluminescence of high density (In, Ga) As/GaP quantum dots
2011
Temperature and excitation intensity dependence of photoluminescence in AlGaN quantum wells with mixed two-dimensional and three-dimensional morphology J. Appl. Phys. 110, 073512 (2011) Strong suppression of internal electric field in GaN/AlGaN multi-layer quantum dots in nanowires Appl. Phys. Lett. 99, 141914 (2011) Decay dynamics of excitonic polarons in InAs/GaAs quantum dots J. Appl. Phys. 110, 074303 (2011) Carrier localization and related photoluminescence in cubic AlGaN epilayers J. Appl. Phys. 110, 063517 (2011) Optical properties of wurtzite/zinc-blende heterostructures in GaN nanowires
Wavelength extension of GaInAs/GaIn(N)As quantum dot structures grown on GaAs
Journal of Crystal Growth, 2003
Self-assembled GaInAs quantum dots (QDs) embedded in GaIn(N)As were grown by atmospheric pressure metalorganic vapor phase epitaxy. The dependence of the photoluminescence (PL) properties on the material composition of the barrier layer was investigated. The emission wavelength and intensity of the QDs could be tuned by controlling the indium and nitrogen compositions in the barrier layer. By using a Ga 0.8 In 0.2 As barrier layer, the roomtemperature PL wavelength of the QDs was extended up to 1.42 mm and the PL intensity was increased by a factor of three compared to the conventional GaInAs/GaAs QD structure. Preliminary results show that by using N-containing Ga 0.85 In 0.15 NAs as a barrier layer instead of Ga 0.85 In 0.15 As an increase in the PL wavelength and intensity in the 1.3 mm wavelength range can be obtained. r