This paper presents a detailed analysis of the dependence of degree of strain relaxation of the self-organized InAs/GaAs quantum dot on the geometrical parameters. Differently shaped quantum dots arranged with differe...This paper presents a detailed analysis of the dependence of degree of strain relaxation of the self-organized InAs/GaAs quantum dot on the geometrical parameters. Differently shaped quantum dots arranged with different transverse periods are simulated in this analysis. It investigates the total residual strain energy that stored in the quantum dot and the substrate for all kinds of quantum dots with the same volume, as well as the dependence on both the aspect ratio and transverse period. The calculated results show that when the transverse period is larger than two times the base of the quantum dots, the influence of transverse periods can be ignored. The larger aspect ratio will lead more efficient strain relaxation. The larger angle between the faces and the substrate will lead more efficient strain relaxation. The obtained results can help to understand the shape transition mechanism during the epitaxial growth from the viewpoint of energy, because the strain relaxation is the main driving force of the quantum dot's self-organization.展开更多
Here we report 1.3μm electrical injection lasers based on InAs/GaAs quantum dots(QDs)grown on a GaAs substrate,which can steadily work at 110-℃without visible degradation.The QD structure is designed by applying the...Here we report 1.3μm electrical injection lasers based on InAs/GaAs quantum dots(QDs)grown on a GaAs substrate,which can steadily work at 110-℃without visible degradation.The QD structure is designed by applying the Stranski-Krastanow growth mode in solid source molecular beam epitaxy.The density of InAs QDs in the active region is increased from 3.8×10^(10)cm^(-2)to 5.9×10^(10)cm^(-2).As regards laser performance,the maximum output power of devices with lowdensity QDs as the active region is 65 m W at room temperature,and that of devices with the high-density QDs is 103 mW.Meanwhile the output power of high-density devices is 131 mW under an injection current of 4 A at 110-℃.展开更多
Semiconductor quantum dots have been intensively investigated because of their fundamental role in solid-state quan- tum information processing. The energy levels of quantum dots are quantized and can be tuned by exte...Semiconductor quantum dots have been intensively investigated because of their fundamental role in solid-state quan- tum information processing. The energy levels of quantum dots are quantized and can be tuned by external field such as optical, electric, and magnetic field. In this review, we focus on the development of magneto-optical properties of single InAs quantum dots embedded in GaAs matrix, including charge injection, relaxation, tunneling, wavefunction distribution, and coupling between different dimensional materials. Finally, the perspective of coherent manipulation of quantum state of single self-assembled quantum dots by photocurrent spectroscopy with an applied magnetic field is discussed.展开更多
The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots( QDs ) grown by molecular-beam epitaxy (MBE) were investigated. The emission wavelength of 1317 nm ...The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots( QDs ) grown by molecular-beam epitaxy (MBE) were investigated. The emission wavelength of 1317 nm was obtained by embedding InAs QDs in InGaAs / GaAs quantum well. The temperature-dependent and time-resolved photoluminescence ( TDPL and TRPL ) were used to study the dynomic characteristics of carriers. InGaAs cap layer may improve the quality of quantum dots for the strain relaxation around QDs, which results in a stronger PL inteasity and an increase of PL peak lifetime up to 170 K. We found that InGaAs buffer layer may reduce the PL peak lifetime of InAs QDs, which is due to the buffer layer accelerating the carrier migration. The results also show that InGaAs cap layer can increase the temperature point when the thermal reemission and nonradiative recombination contribute significantly to the carrier dynamics.展开更多
Photoluminescence (PL) and lasing properties of InAs/GaAs quantum dots (QDs) with different growth procedures prepared by metalorganic chemical vapour deposition are studied. PL measurements show that the low grow...Photoluminescence (PL) and lasing properties of InAs/GaAs quantum dots (QDs) with different growth procedures prepared by metalorganic chemical vapour deposition are studied. PL measurements show that the low growth rate QD sample has a larger PL intensity and a narrower PL line width than the high growth rate sample. During rapid thermal annealing, however, the low growth rate sample shows a greater blueshift of PL peak wavelength. This is caused by the larger InAs layer thickness which results from the larger 2-3 dimensional transition critical layer thickness for the QDs in the low-growth-rate sample. A growth technique including growth interruption and in-situ annealing, named indium flush method, is used during the growth of GaAs cap layer, which can flatten the GaAs surface effectively. Though the method results in a blueshift of PL peak wavelength and a broadening of PL line width, it is essential for the fabrication of room temperature working QD lasers.展开更多
The first operation of an electrically pumped 1.3μm InAs/GaAs quantum-dot laser was previously reported epitaxially grown on Si (100) substrate. Here the direct epitaxial growth condition of 1.3μm InAs/OaAs quantu...The first operation of an electrically pumped 1.3μm InAs/GaAs quantum-dot laser was previously reported epitaxially grown on Si (100) substrate. Here the direct epitaxial growth condition of 1.3μm InAs/OaAs quantum on a Si substrate is further investigated using atomic force microscopy, etch pit density and temperature-dependent photoluminescence (PL) measurements. The PL for Si-based InAs/GaAs quantum dots appears to be very sensitive to the initial OaAs nucleation temperature and thickness with strongest room-temperature emission at 40000 (17Onto nucleation layer thickness), due to the lower density of defects generated under this growth condition, and stronger carrier confinement within the quantum dots.展开更多
The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filt...The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.展开更多
利用液滴外延法在GaAs(001)衬底表面制备InAs量子点,通过控制变量分别研究沉积速率、沉积量对In液滴在GaAs表面生长过程中的影响.使用原子力显微镜(Atomic Force Microscope,AFM)表征I⁃nAs纳米结构形貌,得出结论:(1)沉积速率主要通过影...利用液滴外延法在GaAs(001)衬底表面制备InAs量子点,通过控制变量分别研究沉积速率、沉积量对In液滴在GaAs表面生长过程中的影响.使用原子力显微镜(Atomic Force Microscope,AFM)表征I⁃nAs纳米结构形貌,得出结论:(1)沉积速率主要通过影响In液滴成核率来控制液滴的密度,即随着沉积速率的增大,In原子在衬底表面的成核率增加,InAs量子点密度增加,实验符合生长动力学经典成核理论.(2)沉积量的改变主要影响液滴的熟化过程,即随着沉积量的增大,可参与生长的活跃的In原子增加,促进了液滴熟化,使得扩散坍塌的原子数量增加,导致在InAs纳米结构中出现多量子点现象.展开更多
InAs quantum dots (QDs) grown on InxGa1-xAs/InP matrix by low pressure metal organic vapor phase epitaxy (LP-MOVPE) in nitrogen ambient were studied. Formation of the InAs QDs with different growth conditions was inve...InAs quantum dots (QDs) grown on InxGa1-xAs/InP matrix by low pressure metal organic vapor phase epitaxy (LP-MOVPE) in nitrogen ambient were studied. Formation of the InAs QDs with different growth conditions was investigated. To improve the dot size uniformity, a two-step growth method was used and investigated. It is found that morphology of the InAs QDs formed on such InxGa1-xAs/InP matrix is very sensitive to the growth conditions. InAs QDs with high density of 1.3×1010 cm?2 are grown by using S-K growth method with fast growth rate. Using the two-step growth method, the InAs QDs size uniformity improves by 63% and 110% compared that of the dots grown by ordinary S-K method and ALE method, respectively. Narrow photoluminescence (PL) emission spectrum of the QDs grown by using the two-step growth method is received. FWHM of the PL curve is measured at 26 meV and the peak emission wavelength is larger than 2.3 μm at 77 K.展开更多
The time-resolved photoluminescence and steady photoluminescence (TRPL and PL) spectra on self-assembled InAs/GaAs quantum dots (QDs) are investigated. By depositing GaAs/InAs short period superlattices (SLs), 1.48...The time-resolved photoluminescence and steady photoluminescence (TRPL and PL) spectra on self-assembled InAs/GaAs quantum dots (QDs) are investigated. By depositing GaAs/InAs short period superlattices (SLs), 1.48μm emission is obtained at room temperature. Temperature dependent PL measurements show that the PL intensity of the emission is very steady. It decays only to half as the temperature increases from 15K to room temperature, while at the same time, the intensity of the other emission decreases by a factor of 5 orders of magnitude. These two emissions are attributed to large-size QDs and short period superlattices (SLs), respectively. Large-size QDs are easier to capture and confine carriers, which benefits the lifetime of PL, and therefore makes the emission intensity insensitive to the temperature.展开更多
We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the ...We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).展开更多
The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photol...The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photoluminescence on areal quantum-dot density is systematically investigated as a function of InAs deposition, growth temperature and arsenic pressure. The results of this investigation along with time-resolved photoluminescence measurements show that the com- bination of a growth temperature of 490℃, with a deposition rate of 0.02 ML/s, under an arsenic pressure of 1×10^-6 Torr (1 Torr = 1.33322×10^2 Pa), provides the best compromise between high density and the photoluminescence of quantum dot structure, with a radiative lifetime of 780 ps. The applicability of this 5-layer quantum dot structure to high-repetition-rate pulsed lasers is demonstrated with the fabrication and characterization of a monolithic InAs/GaAs quantum-dot passively mode-locked laser operating at nearly 1300 nm. Picosecond pulse generation is achieved from a two-section laser, with a 19.7-GHz repetition rate.展开更多
Self-organization of PbS into quantum dots superlattices is demonstrated for the first lime, and hexaplanar colloidal crystals 1-10 mu m in size made from PbS quantum dots 4nm in diameter are shown in Transmission Ele...Self-organization of PbS into quantum dots superlattices is demonstrated for the first lime, and hexaplanar colloidal crystals 1-10 mu m in size made from PbS quantum dots 4nm in diameter are shown in Transmission Electron Microscope (TEM) micrograph, and the inner structures of the superlattices can be seen from the High Resolution Transmission Electron Microscope (HRTEM).展开更多
A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on (001) substrate was presented. The three-dimensional finite element analysis for a...A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on (001) substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.展开更多
In this paper, simulation of InAs/GaAs quantum dot (QD) laser is performed based upon a set of eight rate equations for the carriers and photons in five energy states. Carrier dynamics in these lasers were under analy...In this paper, simulation of InAs/GaAs quantum dot (QD) laser is performed based upon a set of eight rate equations for the carriers and photons in five energy states. Carrier dynamics in these lasers were under analysis and the rate equations are solved using 4th order Runge-Kutta method. We have shown that by increasing injected current to the active medium of laser, switching-on and stability time of the system would decrease and power peak and stationary power will be increased. Also, emission in any state will start when the lower state is saturated and remain steady. The results including P-I characteristic curve for the ground state (GS), first excited state (ES1), second excited state (ES2) and output power of the QD laser will be presented.展开更多
利用退火技术 ,实现了在低温 Ga As外延层上 In As量子点的生长 .透射电镜 (TEM)研究表明 ,低温 Ga As外延层上生长的 In As量子点比通常生长的 In As量子点明显变小 ,且密度变大 ,认为是由于低温 Ga As中的点缺陷以及 As沉淀引起的 :...利用退火技术 ,实现了在低温 Ga As外延层上 In As量子点的生长 .透射电镜 (TEM)研究表明 ,低温 Ga As外延层上生长的 In As量子点比通常生长的 In As量子点明显变小 ,且密度变大 ,认为是由于低温 Ga As中的点缺陷以及 As沉淀引起的 :点缺陷释放了部分弹性能 ,使得量子点变小 ,而 As沉淀可能是量子点密度变大的原因 .在光致发光谱 (PL )上 ,退火低温外延层上生长的量子点的发光峰能量较高 。展开更多
基金supported by the National "973" Basic Research Program of China (Grant No 2003CB314901)the National NaturalScience Foundation of China (Grant No 60644004)the 111 Project of China (High School Innovation and Introducing Intellect Project of China) (Grant No B07005)
文摘This paper presents a detailed analysis of the dependence of degree of strain relaxation of the self-organized InAs/GaAs quantum dot on the geometrical parameters. Differently shaped quantum dots arranged with different transverse periods are simulated in this analysis. It investigates the total residual strain energy that stored in the quantum dot and the substrate for all kinds of quantum dots with the same volume, as well as the dependence on both the aspect ratio and transverse period. The calculated results show that when the transverse period is larger than two times the base of the quantum dots, the influence of transverse periods can be ignored. The larger aspect ratio will lead more efficient strain relaxation. The larger angle between the faces and the substrate will lead more efficient strain relaxation. The obtained results can help to understand the shape transition mechanism during the epitaxial growth from the viewpoint of energy, because the strain relaxation is the main driving force of the quantum dot's self-organization.
基金the Science and Technology Program of Guangzhou(Grant No.202103030001)the KeyArea Research and Development Program of Guangdong Province(Grant No.2018B030329001)+8 种基金the National Natural Science Foundation of China(Grant Nos.62035017,61505196,and 62204238)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YJKYYQ20170032)the Major Program of the National Natural Science Foundation of China(Grant Nos.61790580 and 61790581)the Chinese Academy of Sciences and Changchun City Science and Technology Innovation Cooperation Project(Grant No.21SH06)Jincheng Key Research and Development Project(Grant No.20210209)the Key R&D Program of Shanxi Province(Grant No.202102030201004)the R&D Program of Guangdong Province(Grant Nos.2018B030329001 and2020B0303020001)Shenzhen Technology Research Project(Grant No.JSGG20201102145200001)the National Key Technologies R&D Program of China(Grant No.2018YFA0306100)。
文摘Here we report 1.3μm electrical injection lasers based on InAs/GaAs quantum dots(QDs)grown on a GaAs substrate,which can steadily work at 110-℃without visible degradation.The QD structure is designed by applying the Stranski-Krastanow growth mode in solid source molecular beam epitaxy.The density of InAs QDs in the active region is increased from 3.8×10^(10)cm^(-2)to 5.9×10^(10)cm^(-2).As regards laser performance,the maximum output power of devices with lowdensity QDs as the active region is 65 m W at room temperature,and that of devices with the high-density QDs is 103 mW.Meanwhile the output power of high-density devices is 131 mW under an injection current of 4 A at 110-℃.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB921003)the National Natural Science Foundation of China(Grant Nos.11721404,51761145104,and 61675228)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB07030200 and XDPB0803)the CAS Interdisciplinary Innovation Team
文摘Semiconductor quantum dots have been intensively investigated because of their fundamental role in solid-state quan- tum information processing. The energy levels of quantum dots are quantized and can be tuned by external field such as optical, electric, and magnetic field. In this review, we focus on the development of magneto-optical properties of single InAs quantum dots embedded in GaAs matrix, including charge injection, relaxation, tunneling, wavefunction distribution, and coupling between different dimensional materials. Finally, the perspective of coherent manipulation of quantum state of single self-assembled quantum dots by photocurrent spectroscopy with an applied magnetic field is discussed.
文摘The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots( QDs ) grown by molecular-beam epitaxy (MBE) were investigated. The emission wavelength of 1317 nm was obtained by embedding InAs QDs in InGaAs / GaAs quantum well. The temperature-dependent and time-resolved photoluminescence ( TDPL and TRPL ) were used to study the dynomic characteristics of carriers. InGaAs cap layer may improve the quality of quantum dots for the strain relaxation around QDs, which results in a stronger PL inteasity and an increase of PL peak lifetime up to 170 K. We found that InGaAs buffer layer may reduce the PL peak lifetime of InAs QDs, which is due to the buffer layer accelerating the carrier migration. The results also show that InGaAs cap layer can increase the temperature point when the thermal reemission and nonradiative recombination contribute significantly to the carrier dynamics.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60706009, 90401025, 60736036, 60777021 and60476009)the National Key Basic Research Program of China (Grant Nos 2006CB604901 and 2006CB604902)the National High Technology Research and Development Program of China (Grant Nos 2006AA01Z256, 2007AA03Z419 and 2007AA03Z417)
文摘Photoluminescence (PL) and lasing properties of InAs/GaAs quantum dots (QDs) with different growth procedures prepared by metalorganic chemical vapour deposition are studied. PL measurements show that the low growth rate QD sample has a larger PL intensity and a narrower PL line width than the high growth rate sample. During rapid thermal annealing, however, the low growth rate sample shows a greater blueshift of PL peak wavelength. This is caused by the larger InAs layer thickness which results from the larger 2-3 dimensional transition critical layer thickness for the QDs in the low-growth-rate sample. A growth technique including growth interruption and in-situ annealing, named indium flush method, is used during the growth of GaAs cap layer, which can flatten the GaAs surface effectively. Though the method results in a blueshift of PL peak wavelength and a broadening of PL line width, it is essential for the fabrication of room temperature working QD lasers.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11434010,11574356 and 11504415the Funds from the Royal Society,the Defense Science Technology Laboratory and UK Engineering and Physics Research Council
文摘The first operation of an electrically pumped 1.3μm InAs/GaAs quantum-dot laser was previously reported epitaxially grown on Si (100) substrate. Here the direct epitaxial growth condition of 1.3μm InAs/OaAs quantum on a Si substrate is further investigated using atomic force microscopy, etch pit density and temperature-dependent photoluminescence (PL) measurements. The PL for Si-based InAs/GaAs quantum dots appears to be very sensitive to the initial OaAs nucleation temperature and thickness with strongest room-temperature emission at 40000 (17Onto nucleation layer thickness), due to the lower density of defects generated under this growth condition, and stronger carrier confinement within the quantum dots.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61874148,61974141,and 61674020)the Beijing Natural Science Foundation,China(Grant No.4192043)+3 种基金the National Key Research and Development Program of China(Grant No.2018YFB2200104)the Fund from the Beijing Municipal Science&Technology Commission,China(Grant No.Z191100004819012)the Project of the State Key Laboratory of Information Photonics and Optical Communications,Beijing University of Posts and Telecommunications,China(Grant No.IPOC2018ZT01)the 111 Project of China(Grant No.B07005).
文摘The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.
文摘利用液滴外延法在GaAs(001)衬底表面制备InAs量子点,通过控制变量分别研究沉积速率、沉积量对In液滴在GaAs表面生长过程中的影响.使用原子力显微镜(Atomic Force Microscope,AFM)表征I⁃nAs纳米结构形貌,得出结论:(1)沉积速率主要通过影响In液滴成核率来控制液滴的密度,即随着沉积速率的增大,In原子在衬底表面的成核率增加,InAs量子点密度增加,实验符合生长动力学经典成核理论.(2)沉积量的改变主要影响液滴的熟化过程,即随着沉积量的增大,可参与生长的活跃的In原子增加,促进了液滴熟化,使得扩散坍塌的原子数量增加,导致在InAs纳米结构中出现多量子点现象.
文摘InAs quantum dots (QDs) grown on InxGa1-xAs/InP matrix by low pressure metal organic vapor phase epitaxy (LP-MOVPE) in nitrogen ambient were studied. Formation of the InAs QDs with different growth conditions was investigated. To improve the dot size uniformity, a two-step growth method was used and investigated. It is found that morphology of the InAs QDs formed on such InxGa1-xAs/InP matrix is very sensitive to the growth conditions. InAs QDs with high density of 1.3×1010 cm?2 are grown by using S-K growth method with fast growth rate. Using the two-step growth method, the InAs QDs size uniformity improves by 63% and 110% compared that of the dots grown by ordinary S-K method and ALE method, respectively. Narrow photoluminescence (PL) emission spectrum of the QDs grown by using the two-step growth method is received. FWHM of the PL curve is measured at 26 meV and the peak emission wavelength is larger than 2.3 μm at 77 K.
基金Natural Science Foundation of Fujian Province(A992001)
文摘The time-resolved photoluminescence and steady photoluminescence (TRPL and PL) spectra on self-assembled InAs/GaAs quantum dots (QDs) are investigated. By depositing GaAs/InAs short period superlattices (SLs), 1.48μm emission is obtained at room temperature. Temperature dependent PL measurements show that the PL intensity of the emission is very steady. It decays only to half as the temperature increases from 15K to room temperature, while at the same time, the intensity of the other emission decreases by a factor of 5 orders of magnitude. These two emissions are attributed to large-size QDs and short period superlattices (SLs), respectively. Large-size QDs are easier to capture and confine carriers, which benefits the lifetime of PL, and therefore makes the emission intensity insensitive to the temperature.
基金Project supported by the National Natural Science Foundation of China(Grant No.61974141)Tianjin Municipal Science and Technology BureauScience and Technology Innovation Bureau of China-Singapore Tianjin Eco-City。
文摘We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).
基金Project supported by the Natural Science Foundation of Beijing,China (Grant No.4112060)the Special Foundation for National Key Scientific Instrument,China (Grant No.2012YQ140005)+5 种基金the Open Fund of High Power Laser Laboratory,China Academy of Engineering Physics (Grant No.2013HEL03)the National Natural Science Foundation of China (Grant No.61274125)the National Basic Research Program,China (Grant No.2010CB327601)the State Key Laboratory on Integrated Optoelectronics Open Project,China (Grant No.2011KFB002)financially supported by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programmethe financial support through a Royal Academy of Engineering/EPSRC Research Fellowship
文摘The self-assembled growth of InAs/GaAs quantum dots by molecular beam epitaxy is conducted by optimizing several growth parameters, using a one-step interruption method after island formation. The dependence of photoluminescence on areal quantum-dot density is systematically investigated as a function of InAs deposition, growth temperature and arsenic pressure. The results of this investigation along with time-resolved photoluminescence measurements show that the com- bination of a growth temperature of 490℃, with a deposition rate of 0.02 ML/s, under an arsenic pressure of 1×10^-6 Torr (1 Torr = 1.33322×10^2 Pa), provides the best compromise between high density and the photoluminescence of quantum dot structure, with a radiative lifetime of 780 ps. The applicability of this 5-layer quantum dot structure to high-repetition-rate pulsed lasers is demonstrated with the fabrication and characterization of a monolithic InAs/GaAs quantum-dot passively mode-locked laser operating at nearly 1300 nm. Picosecond pulse generation is achieved from a two-section laser, with a 19.7-GHz repetition rate.
文摘Self-organization of PbS into quantum dots superlattices is demonstrated for the first lime, and hexaplanar colloidal crystals 1-10 mu m in size made from PbS quantum dots 4nm in diameter are shown in Transmission Electron Microscope (TEM) micrograph, and the inner structures of the superlattices can be seen from the High Resolution Transmission Electron Microscope (HRTEM).
基金This work was financially supported by the "973" National Basic Research Program of China (No. 2003CB314901)the National "863" High Technology Project of China (No. 2003AA311070)the Open Project of State Key Laboratory on Integrated Opto-electronics.
文摘A systematic investigation of the strain distribution of self-organized, lens-shaped quantum dot in the case of groffth direction on (001) substrate was presented. The three-dimensional finite element analysis for an array of dots was used for the strain calculation. The dependence of the strain energy density distribution on the thickness of the capping layer was investigated in detail when the elastic characteristics of the matrix material were anisotropic. It is shown that the elastic anisotropic greatly influences the stress, strain, and strain energy density in the quantum dot structures. The anisotropic ratio of the matrix material and the combination with different thicknesses of the capping layer, may lead to different strain energy density minimum locations on the capping layer surface, which can result in various vertical ordering phenomena for the next layer of quantum dots, i.e. partial alignment, random alignment, and complete alignment.
文摘In this paper, simulation of InAs/GaAs quantum dot (QD) laser is performed based upon a set of eight rate equations for the carriers and photons in five energy states. Carrier dynamics in these lasers were under analysis and the rate equations are solved using 4th order Runge-Kutta method. We have shown that by increasing injected current to the active medium of laser, switching-on and stability time of the system would decrease and power peak and stationary power will be increased. Also, emission in any state will start when the lower state is saturated and remain steady. The results including P-I characteristic curve for the ground state (GS), first excited state (ES1), second excited state (ES2) and output power of the QD laser will be presented.
文摘利用退火技术 ,实现了在低温 Ga As外延层上 In As量子点的生长 .透射电镜 (TEM)研究表明 ,低温 Ga As外延层上生长的 In As量子点比通常生长的 In As量子点明显变小 ,且密度变大 ,认为是由于低温 Ga As中的点缺陷以及 As沉淀引起的 :点缺陷释放了部分弹性能 ,使得量子点变小 ,而 As沉淀可能是量子点密度变大的原因 .在光致发光谱 (PL )上 ,退火低温外延层上生长的量子点的发光峰能量较高 。