Molecular beam epitaxy (MBE) growth of composite (In,Al)As/(In,Ga)As vertically coupled quantum dots and their application in injection lasers (original) (raw)
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Radiation characteristics of injection lasers based on vertically coupled quantum dots
Superlattices and Microstructures, 1997
We have studied injection lasers based on InGaAs/GaAs vertically coupled quantum dots (QD) grown by molecular beam epitaxy. The threshold current density decreases by one order of magnitude down to 90 A cm −2 (300 K) with an increase of the number of QD stacks (N ) up to 10. For N ≥ 3 lasing occurs via the QD ground state up to room temperature. Differential efficiency increases with N up to 50%. No change in range of high temperature stability of threshold current density (J th ) was observed, while the characteristic temperature (T 0 ) measured at 300 K increases from 60 to 120 K. Using InGaAs-AlGaAs QD with higher localization energy allowed us to decrease J th down to 60 A cm −2 and to increase the differential efficiency up to 70%.
Journal of Crystal Growth, 2003
We have systematically studied the effects of incorporation of Al in the embedding layers of self-organized InAs quantum dots (QDs) grown on GaAs(0 0 1) by molecular-beam epitaxy on their density and structural and optical properties. When using an In 0.1 Al x Ga 0.9Àx As lower embedding layer (x ¼ 0:001-0.1) we observe a large increase in QD density with increasing x: The increase is much larger than when increasing the In content in a conventional In x Ga 1Àx As (x ¼ 020.2) lower embedding layer. We attribute the differences to different nucleation mechanisms. Furthermore, introducing a thin InAlAs upper embedding layer results in strong 1.3 mm emission with a large energy separation between the ground and the first excited state transitions.
Journal of Crystal Growth, 2004
Self-assembled InAs quantum dots (QDs) with In 0.15 Ga 0.85 As were grown by a molecular beam epitaxy and their optical properties were investigated by photoluminescence (PL) spectroscopy. For InAs QDs inserted in an asymmetric In 0.15 Ga 0.85 As quantum well, the emission peak position of QDs is 1.30 mm (0.953 eV) with narrower PL linewidth and larger energy-level spacing between the ground states and the first excited states compared to those of QDs embedded in a GaAs matrix. While the room temperature PL yield for InAs QDs in a GaAs matrix was reduced by 1/99 from that measured at 18 K, the reduction in PL yield for InAs QDs, grown on a 1 nm In 0.15 Ga 0.85 As layer, with a 6 nm In 0.15 Ga 0.85 As overgrowth layer was only 1/27. Also, using the In 0.15 Ga 0.85 As overgrowth layer significantly reduced the temperature sensitivity of the peak energy for InAs QDs. The relatively better temperature PL characteristics of the QDs with In 0.15 Ga 0.85 As, as well as the ability to control the emission peak position and the energy-level spacing are interesting and important for device applications. r
(In,Ga)As/GaP electrical injection quantum dot laser
Applied Physics Letters, 2014
The paper reports on the realization of multilayer (In,Ga)As/GaP quantum dot (QD) lasers grown by gas source molecular beam epitaxy (GSMBE). The QDs have been embedded in (Al,Ga)P/GaP waveguide structures. Laser operation at 710 nm is obtained for broad area laser devices with a
Low-threshold injection lasers based on vertically coupled quantum dots
Journal of Crystal Growth, 1997
We have fabricated and studied injection lasers based on vertically coupled quantum dots (VECODs). VECODs are self-organized during successive deposition of several sheets of (In,Ga)As quantum dots separated by thin GaAs spacers. VECODs are introduced in the active region of a GaAs-A1GaAs GRIN SCH lasers. Increasing the number of periods (N) in the VECOD leads to a remarkable decrease in threshold current density ( ~ 100 A/cm 2 at 300 K for N = 10). Lasing proceeds via the ground state of the quantum dots (QD) up to room temperature. Placing the QD array into an external AIGaAs--GaAs quantum well allows us to extend the range of thermal stability of threshold current density (To = 350 K) up to room temperature. Using (In,Ga)As-(A1,Ga)As VECODs in combination with high temperature growth of emitter and waveguide layers results in further reduction of threshold current density (60-80 A/cm 2, 300 K) and increase in internal quantum efficiency (70%). Room temperature continuous wave operation (light output 160 mW per mirror) and lasing via the states of QDs up to I = (6-7) Ith have been demonstrated.
MBE growth and characterisation of InGaAs quantum dot lasers
Materials Science and Engineering: B, 2000
High quality self-assembled InGaAs quantum dots have been formed on GaAs by molecular beam epitaxy via Stranski-Krastonov growth mode, and have been employed to produce quantum dot lasers with reasonably good properties. The effects of growth conditions, substrate misorientation, and doping in quantum dots on the characteristics of quantum dots and quantum dot lasers are presented. It has been shown that higher density of quantum dots is obtained under higher As flux because the diffusion length of Ga adatoms is reduced. Higher degree of substrate misorientation also leads to higher density of quantum dots since the kinks on the surface have similar effect on the diffusion of cations. It is also found that doping in the quantum dots plays an important role in the performance of quantum dot lasers. Room temperature continuous wave operation has been achieved on Be-doped quantum dot lasers. Under pulse operation, characteristic temperature as high as 121 K between 20 and 70°C has been obtained.
Solid-State Electronics, 1998
AbstractÐThe properties of the self-organized In 0.5 Ga 0.5 As quantum dots on In 0.1 Ga 0.9 As, GaAs, and In 0.1 Al 0.9 As surfaces and matrices are investigated using atomic force microscopy (AFM) and photoluminescence (PL). It is found that both the size variation and the density of the quantum dots depend closely on the matrix materials. PL spectra indicate that the In 0.5 Ga 0.5 As quantum dots in In 0.1 Ga 0.9 As matrix exhibit higher intensity as compared to those in GaAs and In 0.1 Al 0.9 As matrices. It is also found that the activation energy of the In 0.5 Ga 0.5 As quantum dots in GaAs matrix is higher than that of the dots in In 0.1 Ga 0.9 As matrix. Whereas the quantum dots in In 0.1 Al 0.9 As matrix exhibit the lowest activation energy due to higher carrier hopping probability and defect density. #
Nano-engineering approaches to self-assembled InAs quantum dot laser medium
Journal of Electronic Materials, 2006
An umber of nano-engineering methods are proposed and tested to improve optical properties of alaser gain medium using the self-assembled InAs quantum dot (QD) ensemble. The laser characteristics of concerni nclude higher gain, larger modulation bandwidth, highere fficiency at elevated temperatures,h ighert hermal stability, and enhanced reliability. The focus of this paper is on the management of QD properties throughd esign and molecular beam epitaxial growth and modification of QD heterostructures.This includes digital alloysa sh igh-quality wide-bandgap barrier;u nder-and overlayers with various compositions to control thed ynamics of QD formation and evolution on the surface; shape engineering of QDs to improve electron-hole overlapa nd reduce inhomogeneous broadening; band engineering of QD heterostructures to enhance the carrierl ocalization by reduction of thermal escapef rom dots; as well as tunnel injection from quantum wells( QWs) to accelerate carriert ransfer to the lasing state. Beneficial properties of the developedQ Dm edia are demonstrated at room temperature in laser diodes with unsurpassedthermal stabilitywithacharacteristic temperatureof380 K, high waveguide modal gain . 50 cm ÿ 1 ,u nsurpassed defect toleranceo vert wo orderso fm agnitude highert han that of QWs typically used in lasers, and efficient emission from at wo-dimensional (2-D)p hotonic crystal nanocavity.
Applied Surface Science, 2002
The development of molecular-beam epitaxy (MBE) of GaAs/AlGaAs heterostructures, used for fabrication of $9 mm quantum cascade lasers (QCLs), is reported. The X-ray diffractometry (XRD) structural characterization, as an integral part of this process, is presented as well. Some conclusions, concerning the relationships between the used type of epitaxial technology and the necessity of special procedures of growth rate (V gr ) calibration, are reached. The influence of the structural features of the QCL active region on the electronic band structure is calculated, and consequently some predictions as to the device electrical properties are presented as well.