Photoluminescence study of (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum well grown by molecular beam epitaxy

Photoluminescence study of (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum wells (BQWs) grown by molecular beam epitaxy (MBE) were carried out. Temperature and excitation power dependent photoluminescence (PL) study indicated that the band alignment of the BQWs is type - II. The origin of the double-peak luminescence was discussed. Under optimized growth conditions, the PL emission wavelength from the BQWs has been extend up to 1.31 mu m with a single peak at room temperature.

Molecular beam epitaxy growth and photoluminescence study of room temperature 1.31 mu m (InyGa1-yAs/GaAs1-x Sb-x)/ GaAs bilayer quantum wells

Molecular beam epitaxy (MBE) growth of (InyGa1-yAs/GaAs1-xSbx)/GaAs bilayer quantum well (BQW) structures has been investigated. It is evidenced by photo luminescence (PL) that a strong blue shift of the PL peak energy of 47 meV with increasing PL excitation power from 0.63 to 20 mW was observed, indicating type II band alignment of the BQW. The emission wavelength at room temperature from (InyGa1-yAs/GaAs1-xSbx)/GaAs BQW is longer (above 1.2 μ m) than that from InGaAs/GaAs and GaAsSb/GaAs SQW structures (1.1 μ m range), while the emission efficiency from the BQW structures is comparable to that of the SQW. Through optimizing growth conditions, we have obtained room temperature 1.31 μ m wavelength emission from the (InyGa1-yAs/GaAs1-xSbx)/GaAs BQW. Our results have proved experimentally that the GaAs-based bilayer (InyGa1-yAs/GaAs1-xSbx)/GaAs quantum well is a useful structure for the fabrication of near-infrared wavelength optoelectronic devices. © 2005 Elsevier B.V. All rights reserved.

Room temperature 1.25 mu m emission from high indium content InxGa1-xAs/GaAs quantum wells grown by molecular beam epitaxy

Long-wavelength high indium content InxGa1-xAs/GaAs single/multi quantum wells (QWs) structures have been successfully grown by molecular beam epitaxy. It is evidenced by X-ray measurements that the critical thickness of the well width of InxGa1-xAs/GaAs QWs with an indium content x of 47.5% can be raised up to 7nm without strain relation. 1.25μ m photoluminescence (PL) emission is obtained from the QWs with narrower full-width at half maximum (FWHM) less than 30meV. Our results are important basements which are useful for further fabricating GaAs-based long-wavelength devices. © 2005 Elsevier B.V. All rights reserved.

Optimization of GaInNAs(Sb)/GaAs quantum wells at 1.3-1.55 mu m grown by molecular beam epitaxy

The InGaNAs(Sb)/(GaNAs)/GaAs quantum wells (QWs) emitting at 1.3-1.55 mu m have been grown by molecular beam epitaxy (MBE). The parameters of the radio frequency (RF) such as RF power and flow rate are optimized to reduce the damages from the ions or energetic species. The growth temperature is carefully controlled to prevent the phase segregation and strain relaxation. The effects of Sb on the wavelength and quality are investigated. The GaNAs barrier is used to extend the wavelength and reduce the strain. A 1.5865 mu m InGaNAs(Sb)/GaNAs SQW edge emitting laser lasing at room temperature at continuous wave operation mode is demonstrated. (c) 2006 Elsevier B.V. All rights reserved.

Metamorphic growth of 1.25-1.29 mu m InGaAs quantum well lasers on GaAs by molecular beam epitaxy

We demonstrate 1.25-1.29 mu m metamorphic laser diodes grown on GaAs by molecular beam epitaxy (MBE) using an alloy-graded buffer layer (GBL). Use of Be in the GBL is effective to reduce surface/interface roughness and improves optical quality. The RMS surface roughness of the optimized metamorphic laser is only two atomic monolayers for 1 x 1 mu m(2). Cross-sectional transmission electron microscopy (TEM) images confirm that most dislocations are blocked in the GBL. Ridge waveguide lasers with 4 mu m wide ridge were fabricated and characterized. The average threshold current under the pulsed excitation is in 170-200 mA for a cavity length of 0.9-1.5 mm. This value can be further reduced to about 100 mA by high-reflectivity coating. Lasers can work in an ambient temperature up to at least 50 degrees C. (c) 2006 Elsevier B.V. All rights reserved.

Application of rapid thermal annealing on 1.3-1.55 mu m GaInNAs(Sb) lasers grown by molecular beam epitaxy

Rapid thermal annealing (RTA) has been demonstrated as an effective way to improve the crystal quality of GaInNAs(Sb) quantum wells (QWs). However, few investigations have been made into its application in laser growth and fabrication. We have fabricated 1.3 mu m GaInNAs lasers, both as -grown and with post-growth RTA. Enhanced photoluminescence (PL) intensity and decreased threshold current are obtained with RTA, but the characteristic temperature T-o and slope efficiency deteriorate. Furthermore, T-o has an abnormal dependence on the cavity length. We attribute these problems to the deterioration of the wafer's surface. RTA with deposition Of SiO2 was performed to avoid this deterioration, T-o was improved over the samples that underwent RTA without SiO2. Post-growth and in situ annealing were also investigated in a 1.55 mu m GaInNAsSb system. Finally, continuous operation at room temperature of a GaAs-based dilute nitride laser with a wavelength over 1.55 mu m was realized by introducing an in situ annealing process. (c) 2007 Elsevier B.V. All rights reserved.

Evolution of InAs/GaAs(001) islands during the two- to three-dimensional growth mode transition in molecular-beam epitaxy

A detailed observation was made using atomic force microscopy on the two- to three-dimensional (2D-3D) growth mode transition in the molecular-beam epitaxy of InAs/GaAs(001). The evolution of the 3D InAs islands during the 2D-3D mode transition was divided into two successive phases. The first phase may be explained in terms of a critical phenomenon of the second-order phase transition.

Growth of GaSb layers on GaAs (001) substrate by molecular beam epitaxy

GaSb 1 mu m-thick layers were grown by molecular beam epitaxy on GaAs (001). The effects of the growth conditions on the crystalline quality, surface morphology, electrical properties and optical properties were studied by double crystalline x-ray diffraction, atomic force microscopy, Hall measurement and photoluminescence spectroscopy, respectively. It was found that the surface roughness and hole mobility are highly dependent on the antimony-to-gallium flux ratios and growth temperatures. The crystalline quality, electrical properties and optical properties of GaSb layers were also studied as functions of growth rate, and it was found that a suitably low growth rate is beneficial for the crystalline quality and electrical and optical properties. Better crystal quality GaSb layers with a minimum root mean square surface roughness of 0.1 nm and good optical properties were obtained at a growth rate of 0.25 mu m h(-1).

Molecular beam epitaxy InAs dot arrays on InGaAs/GaAs

Periodical alignment of the InAs dots along the < 100 > and < 110 > directions was observed on an elastically relaxed InGaAs buffer layer grown at 500 and 450 degrees C, respectively, on the vicinal GaAs(001) substrate. Due to alignment along these directions, the InAs dots were arranged into a quasi-two-dimensional hexagonal lattice. Such a periodical arrangement of InAs dots may be explained in terms of modulation in strain as well as composition along [110] as observed by using cross-sectional transmission electron microscopy.

Electrical properties of undoped In0.53Ga0.47As grown on InP substrates by molecular beam epitaxy

A series of 1-mu m-thick undoped In0.53Ga0.47As with different substrate growth temperature (T-g) or different beam flux pressure (BFP) of As were grown on lattice-matched semi-insulating InP (001) substrates by molecular beam epitaxy (MBE). Van der Pauw Hall measurements were carried out for these In0.53Ga0.47As samples. The residual electron concentration decreased with increasing temperature from 77 to 140 K, but increased with increasing temperature from 140 to 300 K. Rapid thermal annealing (RTA) can reduce the residual electron concentration. The residual electron mobility increased with increasing temperature from 77 to 300 K. All these electrical properties are associated with As antisite defects. (c) 2006 Elsevier B.V. All rights reserved.

Nanoelectronic devices-resonant tunnelling diodes grown on InP substrates by molecular beam epitaxy with peak to valley current ratio of 17 at room temperature

This paper reports that lnAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm(2) has been obtained for diodes with AlAs barriers of ten monolayers, and an In0.53Ga0.47As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.

The role of Sb in the molecular beam epitaxy growth of 1.30-1.55 mu m wavelength GaInNAs/GaAs quantum well with high indium content

Sb-assisted GaInNAs/GaAs quantum wells (QWs) with high (42.5%) indium content were investigated systematically. Transmission electron microscopy, reflection high-energy electron diffraction and photoluminescence (PL) measurements reveal that Sb acts as a surfactant to suppress three-dimensional growth. The improvement in the 1.55 mu m range is much more apparent than that in the 1.3 mu m range.. which can be attributed to the difference in N composition. The PL intensity and the full-width at half maximum of the 1.55 mu m single-QW were comparable with that of the 1.3 Am QWs. (c) 2006 Elsevier B.V. All rights reserved.

Optical properties of inGaAs/GaAs quantum wells grown by Sb-assisted molecular beam epitaxy

It is found that both methods using either continuous Sb supply or pre-deposition of a very thin Sb layer are efficient for the Sb-assisted molecular beam epitaxy growth of highly strained InGaAs/GaAs quantum wells (QWs). The emission of QWs is extended to long wavelength close to 1.25 mu m with high luminescence efficiency at room temperature. The influence of rapid thermal annealing (RTA) on the photoluminescence intensity critically depends on the annealing temperature and duration for highly strained QWs. A relatively low RTA temperature of 700 degrees C with a short duration of 10 s is suggested for optimizing the annealing effect. (c) 2005 Elsevier B.V. All rights reserved.

Characteristic of rapid thermal annealing on GaIn(N)(Sb)As/GaAs quantum well grown by molecular-beam epitaxy

Effect of rapid thermal annealing on photoluminescence (PL) properties of InGaAs, InGaNAs, InGaAsSb, and InGaNAsSb quantum wells (QWs) grown by molecular-beam epitaxy was systematically investigated. Variations of PL intensity and full width at half maximum were recorded from the samples annealed at different conditions. The PL peak intensities of InGaAs and InGaNAs QWs initially increase and then decrease when the annealing temperature increased from 600 to 900 degrees C, but the drawing lines of InGaAsSb and InGaNAsSb take on an "M" shape. The enhancement of the PL intensity and the decrease of the full width at half maximum in our samples are likely due to the removal of defects and dislocations as well as the composition's homogenization. In the 800-900 degrees C high-temperature region, interdiffusion is likely the main factor influencing the PL intensity. In-N is easily formed during annealing which will prevent In out diffusion, so the largest blueshift was observed in InGaAsSb in the high-temperature region. (c) 2006 American Institute of Physics.

Growth of low-density InAs/GaAs quantum dots on a substrate with an intentional temperature gradient by molecular beam epitaxy

InAs was deposited by molecular beam epitaxy (MBE) on a GaAs substrate with an intentional temperature gradient from centre to edge. Two-dimensional (2D) to three-dimensional (3D) morphology evolution was found along the direction in which the substrate temperature was decreasing. Quantum dots (QDs) with density as low as similar to 8 x 10(6) cm(-2) were formed in some regions. We attribute the morphological evolution to the temperature-dependent desorption of deposited indium and the intermixing between deposited indium and gallium from the buffer.