Showing papers on "Quantum well published in 1993"
TL;DR: The literature on quantum-well infrared photodetectors (QWIPs) is reviewed in this paper, where a detailed discussion is given on the device physics of the intersubband absorption and hot-carrier transport processes for individual detectors, as well as the high performance which has been achieved for large staring arrays.
Abstract: The extensive literature on quantum‐well infrared photodetectors (QWIPs) is reviewed. A detailed discussion is given on the device physics of the intersubband absorption and hot‐carrier transport processes for individual detectors, as well as the high performance which has been achieved for large staring arrays. QWIPs having widely different structures, materials, and spectral responses are covered, as is the optimization of the quantum‐well parameters for maximum performance.
1,471 citations
Book•
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01 Jan 1993
TL;DR: In this article, the origin of Quantum Wells and the Quantum Well Laser is discussed and the effect of intrinsic relaxation on optical spectra is discussed, as well as the properties of Quantum Well Lasers.
Abstract: Foreword: The Origin of Quantum Wells and the Quantum Well Laser. Optical Gain in III-V Bulk and Quantum Well Semiconductors. Intraband Relaxation Effect on Optical Spectra. Multiquantum Well Lasers: Threshold Considerations. Ultra-Low Threshold Quantum Well Lasers. Dynamics of Quantum Well Lasers. Single Quantum Well Ingaasp and Algaas Lasers: A Study of Some Peculiarities. Valence Band Engineering in Quantum Well Lasers. Strained Layer Quantum Well Heterostructure Lasers. Algainp Quantum Well Lasers. Quantum Wire Semiconductor Lasers. Chapter References. Index.
559 citations
TL;DR: Modulation spectroscopy is a powerful method for the study and characterization of a large number of semiconductor configurations, including bulk/thin film, microstructures (heterojunctions, quantum wells, superlattices, quantum dots), surfaces/interfaces and actual device structures in addition to semiconductor growth/processing as mentioned in this paper.
Abstract: Modulation spectroscopy is a powerful method for the study and characterization of a large number of semiconductor configurations, including bulk/thin film, microstructures (heterojunctions, quantum wells, superlattices, quantum dots), surfaces/interfaces and actual device structures in addition to semiconductor growth/processing. Furthermore, the influence of external perturbations such as temperature, electric fields, hydrostatic pressure, uniaxial stress, etc. can be investigated. This optical technique utilizes a very general principle of experimental physics, in which a periodically applied perturbation (either to the sample or probe) leads to sharp, derivative-like spectral features in the optical response of the system. Because of the richness of the derivative-like spectra, the information in the lineshape fits, room temperature performance and relative simplicity of operation this method is becoming increasingly more important as a tool to study these materials and structures. This article will review developments in the field during the last decade.
338 citations
TL;DR: A range of techniques, based on impurity diffusion, dielectric capping and laser annealing, have been developed to enhance the quantum well intermixing (QWI) rate in selected areas of a wafer as discussed by the authors.
Abstract: Intermixing the wells and barriers of quantum well structures generally results in an increase in the band gap and is accompanied by changes in the refractive index. A range of techniques, based on impurity diffusion, dielectric capping and laser annealing has been developed to enhance the quantum well intermixing (QWI) rate in selected areas of a wafer; such processes offer the prospect of a powerful and relatively simple fabrication route for integrating optoelectronic devices and for forming photonic integrated circuits (PICS). Recent progress in QWI techniques is reviewed, concentrating on processes which are compatible with PIC applications, in particular the achievement of low optical propagation losses.
317 citations
TL;DR: The absence of band-gap renormalization in the laser emission indicates a marked increase in the stability of the exciton in one dimension.
Abstract: Stimulated optical emission from the lowest exciton state in atomically smooth semiconductor quantum wires is observed for the first time. The wires are formed by the ssT intersection of two 7 nm GaAs quantum wells. The optical emission wavelength is nearly independent of pump levels. This absence of band-gap renormalization in the laser emission indicates a marked increase in the stability of the exciton in one dimension.
255 citations
TL;DR: In this article, the authors reported the observation of bistable polarization switching in a vertical-cavity surface-emitting laser under optical injection and measured the wavelength dependence of the switching.
Abstract: We report the observation of bistable polarization switching in a vertical‐cavity surface‐emitting laser under optical injection. The wavelength dependence of the switching is measured. It is found that this polarization switching is achieved through injection locking where both the wavelength and the polarization of the vertical‐cavity laser are locked to the injected optical signal.
240 citations
TL;DR: In this article, the authors describe the performance of blue-green injection laser with Zn1−xMgxSySe1−y cladding layers and demonstrate that the use of ZnSzSe1+y claddings provides a clear improvement in optical confinement, demonstrated by the widening of the far field pattern in the direction perpendicular to the layers.
Abstract: We describe the performance of blue‐green injection lasers containing Zn1−xMgxSySe1−y cladding layers. The devices have yielded the lowest reported threshold current densities (500 A/cm2) and the highest reported pulsed output powers (500 mW) at room temperature. Lasing has been observed at temperatures as high as 394 K. The room temperature and 85 K lasing wavelengths are 516 and 496 nm, respectively. The use of Zn1−xMgxSySe1−y, instead of ZnSzSe1−z, cladding layers provides a clear improvement in optical confinement, demonstrated by the widening of the far‐field pattern in the direction perpendicular to the layers. The lasers are separate‐confinement heterostructures with a ZnS0.06Se0.94 waveguiding region and a single Cd0.2Zn0.8Se strained quantum well. The entire structure is pseudomorphic with the GaAs substrate.
225 citations
Book•
01 Jan 1993
TL;DR: In this article, the authors explore recent developments with InGaAs and provide promising applications in the fields of microelectronics and optoelectronics, including structural, thermal, mechanical and vibrational properties, the band structure of lattice-matched and strained alloys, transport and surface properties, radiative and non-radiative recombinations, expitaxial growth, doping, etching of InGAAs and related heterostructures, photodetectors, FETs, double heterostructure and quantum well lasers.
Abstract: The semiconductor InGaAs (indium gallium arsenide) plays a pivotal role in the study of quantum systems which provide promising applications in the fields of microelectronics and optoelectronics. This reference explores recent developments with InGaAs. Leading researchers from the USA, Europe and Japan cover such issues as structural, thermal, mechanical and vibrational properties, the band structure of lattice-matched and strained alloys, transport and surface properties, radiative and non-radiative recombinations, expitaxial growth, doping, etching of InGaAs and related heterostructures, photodetectors, FETs, double heterostructure and quantum well lasers.
212 citations
TL;DR: In this article, a wet chemical synthetic route is presented for the preparation of a spherical quantum well, which consists of a core of size-quantized CdS, a monolayer of HgS and approximately four monolayers of CcS as the outermost shell.
204 citations
TL;DR: In this article, the authors describe methods for directional coupling of light output from whisperinggallery mode microdisk lasers using patterned asymmetries in the shape of microdisk resonators.
Abstract: We describe methods for directional coupling of light output from whispering‐gallery mode microdisk lasers. Patterned asymmetries in the shape of microdisk resonators provide control of both direction and intensity of light output without dramatically increasing laser thresholds.
192 citations
TL;DR: The physical properties of GaSb are briefly presented and the device implications reviewed in this paper, where a direct gap semiconductor (0.72 eV) capable of being doped either p or n type with good mobilities and it has significant electrooptical potential in the near IR range.
Abstract: The physical properties of GaSb are briefly presented and the device implications reviewed. GaSb is a direct gap semiconductor (0.72 eV) capable of being doped either p or n type with good mobilities and it has significant electro-optical potential in the near IR range. As a substrate, or active layer, GaSb can be employed in conjunction with many semiconductors such as (AlGa)Sb or In(AsSb) and has interesting heterojunction potential for detectors and lasers and quantum well structures.
TL;DR: In this article, a gas-phase diffusion model based on Laplace's equation was used to analyze the thickness and compositional variations caused by selective growth of InP, InGaAs, GaInAsP and quantum well material on planar substrates patterned with silica masks.
Abstract: Low-pressure MOCVD has been used to grow layers of InP, InGaAs, GaInAsP and quantum well material on planar substrates patterned with silica masks. The thicknesses and, where relevant, the compositions of these selectively grown layers were investigated by optical and scanning electron microscopy, surface profiling, energy dispersive X-ray analysis, secondary-ion mass spectroscopy and spatially resolved photoluminescence. The epitaxial layers were found to be both thicker and richer in indium in the vicinity of a mask. The perturbations in the thickness and composition of material grown around a given mask pattern were independent of the orientation of the pattern with respect to the gas flow and the crystallographic axes of the substrate. Lateral movement of material from the masked regions to the surrounding areas was found to take place in the gas above the water surface. A gas-phase diffusion model based on Laplace's equation was used to analyze the thickness and compositional variations caused by selective growth. The emission wavelength of selectively grown InGaAs/GaInAsP MQW material was shifted by over 100 nm without degradation in emission efficiency. The lasing wavelength of Fabry-Perot lasers fabricated on such material was increased by a similar amount without degradation of threshold current.
TL;DR: In this article, the peak wavelength of the quantum well has been offset from the wavelength of device cavity mode so that they are aligned at elevated temperatures, and the result of this design change is to produce an 8 mu m-diameter VCSEL capable of operation to 145 degrees C, as well as CW operation of broad-area (70- mu m diameter) heat-sunk devices.
Abstract: The temperature dependence and power output of vertical-cavity surface-emitting lasers (VCSELs) are addressed. The peak wavelength of the quantum well has been offset from the wavelength of the device cavity mode so that they are aligned at elevated temperatures. The result of this design change is to produce an 8- mu m-diameter VCSEL capable of operation to 145 degrees C, as well as CW operation of broad-area (70- mu m diameter) heat-sunk devices to record power levels. Fiber coupling experiments were also carried out, and a record 33-mW CW power was coupled to a multimode fiber. >
TL;DR: In this article, a method for calculating the electronic states and optical properties of multidimensional semiconductor quantum structures is described, which is applicable to heterostructures with confinement in any number of dimensions: e.g. bulk, quantum wells, quantum wires and quantum dots.
Abstract: A method for calculating the electronic states and optical properties of multidimensional semiconductor quantum structures is described. The method is applicable to heterostructures with confinement in any number of dimensions: e.g. bulk, quantum wells, quantum wires and quantum dots. It is applied here to model bulk and multiquantum well (MQW) InGaAsP active layer quaternary lasers. The band parameters of the quaternary system required for the modeling are interpolated from the available literature. We compare bulk versus MQW performance, the effects of compressive and tensile strain, room temperature versus high temperature operation and 1.3 versus 1.55 pm wavelength operation. Our model shows that: compressive strain improves MQW laser performance. MQW lasers have higher amplification per carrier and higher differential gain than bulk lasers, however, MQW performance is far from ideal because of occupation of non-lasing minibands. This results in higher carrier densities at threshold than in bulk lasers, and may nullify the advantage of MQW lasers over bulk devices for high temperature operation. >
TL;DR: In this article, a detailed carrier dynamics model for quantum well lasers is presented, which describes the transport of carriers using full continuity equations and the gain by rate equations for each well separately, and also takes into account electron-hole interactions which modify the energy band structure.
Abstract: A detailed carrier dynamics model for quantum well lasers is presented. The model describes the transport of carriers using full continuity equations and the gain by rate equations for each well separately, and it also takes into account electron-hole interactions which modify the energy band structure. To this end, the model includes Poisson and Schrodinger equations. The model is solved in steady state where it yields nonuniform carrier distributions along the crystal growth axis. Dynamically, the model is solved in the time domain, yielding the evolution of carriers in time and space and highlighting a new effect, photon-assisted carrier transport. The model is also solved in the small-signal regime where the phase lag in gain between wells is determined. >
TL;DR: In this paper, the authors investigated changes in the modulation response, the differential gain delta g/ delta n, the nonlinear gain coefficient in, and the damping factor K, which result from three structural modifications to GaAs-based multiple quantum well lasers.
Abstract: Utilizing small-signal direct modulation and relative intensity noise measurements, the authors investigate changes in the modulation response, the differential gain delta g/ delta n, the nonlinear gain coefficient in , and the damping factor K, which result from three structural modifications to GaAs-based multiple quantum well lasers: the addition of strain in the quantum wells; and increase in the number of quantum wells; and the addition of p-doping in the quantum wells. These modifications are assessed in terms of their potential for reducing the drive current required to achieve a given modulation bandwidth, for increasing the maximum intrinsic modulation bandwidth of the laser, and for improving the prospects for monolithic layer/transistor integration. It has been possible to simultaneously increase delta g/ delta n and decrease K, yielding very efficient high-speed modulation (20 GHz at a DC bias current of 50 mA) and the first semiconductor lasers to achieve a direct modulation bandwidth of 30 GHz under DC bias. >
NEC1
TL;DR: In this article, a mask-patterned planar planar InP substrate is used to grow InGaAsP/InP layers on typically 2 μm wide open stripe regions between pairs of SiO 2 mask stripes.
TL;DR: In this paper, the effect of strain on Auger recombination has been studied using the differential carrier lifetime technique in both lattice matched InGaAs-InP and compressively strained quaternary quantum wells.
Abstract: The effect of strain on Auger recombination has been studied using the differential carrier lifetime technique in both lattice matched InGaAs-InP and compressively strained quaternary quantum wells. It is found that Auger recombination is reduced in strained devices. The transparency carrier density and differential gain of both lattice matched and strained devices have been obtained by gain and relative intensity noise measurement. A reduction of the transparency carrier density is observed in the strained device. However, no differential gain increase is seen. The temperature sensitivity of the threshold current density of both lattice matched and strained devices has been fully studied. Physical parameters contributing to the temperature sensitivity of the threshold current density have been separately measured, and it is shown that the change in differential gain with temperature is a dominant factor in determining the temperature sensitivity of both lattice matched and strained devices. >
01 Jan 1993
TL;DR: In this paper, a review of the techniques for laser cooling and trapping of neutral atoms are described. But it was not until the 1980's that optical momentum transfer was used to cool and trap neutral atoms.
Abstract: Abstract As early as 1917, Einstein had predicted that momentum is transferred in the absorption and emission of light, but it was not until the 1980's that such optical momentum transfer was used to cool and trap neutral atoms. By properly tuning laser light close to atomic transitions, atomic samples can be cooled to extremely low temperatures, the brightness of atomic beams can be enhanced to unprecedented values, and atoms can be manipulated with extraordinary precision. In this review several of the techniques for laser cooling and trapping of neutral atoms are described.
TL;DR: A long wavelength, low-energy excitation of the fractional quantum Hall state at υ=1/3 has been observed by inelastic light scattering and its energy is consistent with theoretical predictions for the collective gap excitations of the incompressible quantum fluid.
Abstract: A long wavelength, low-energy excitation of the fractional quantum Hall state at \ensuremath{
u}=1/3 has been observed by inelastic light scattering. The mode appears as a very sharp peak with marked temperature and magnetic field dependence. Its energy is consistent with theoretical predictions for the collective gap excitations of the incompressible quantum fluid. Spectra interpreted as q=0 collective spin-wave excitations also display the strong dependence on field and temperature associated with the fractional quantum Hall state.
TL;DR: The binding energies of donors in both finite and infinite GaAs•(Ga,Al)As spherical quantum dots are calculated as a function of the donor position for different radii within the effective mass approximation.
Abstract: The binding energies of hydrogenic donor in both finite and infinite GaAs‐(Ga,Al)As spherical quantum dots are calculated as a function of the donor position for different radii within the effective‐mass approximation. It is observed an enhancement of the binding energy of donors in quantum dots when compared to results in quantum wells and quantum‐well wires, which is an expected consequence of the higher geometrical electronic confinement in these systems. The density of impurity states as a function of the donor binding energy was also calculated. As a general feature it presents structures associated with special impurity positions that may be important in the understanding of the absorption and photoluminescence experiments of doped quantum dots.
TL;DR: In this article, the authors studied the variation in DC photocurrent with bias and temperature from GaAs-Al/sub x/Ga/sub 1-x/As single quantum wells embedded in p-i-n diodes and found that the observed temperature response shows Arrhenius behaviour with a field-dependent activation energy close to the hole well depth.
Abstract: The authors have studied the variation in DC photocurrent with bias and temperature from GaAs-Al/sub x/Ga/sub 1-x/As single quantum wells embedded in p-i-n diodes. They found that the observed temperature response shows Arrhenius behaviour with a field-dependent activation energy close to the hole well depth. This can be accounted for using a model based on the competition between photocarrier escape and recombination. Using reasonable values for the diode's built-in voltage and the quantum-well recombination lifetime, good quantitative agreement between theory and experiment is achieved if it is assumed that the recombination rate is governed by the fastest escaping carriers, which are light holes in the present devices. >
TL;DR: It is demonstrated that this work can enhance, weaken, and also phase shift terahertz (THz) radiation emitted by optically excited quantum beats in a coupled quantum well.
Abstract: We demonstrate that we can enhance, weaken, and also phase shift terahertz (THz) radiation emitted by optically excited quantum beats in a coupled quantum well. The changes in the evolution of the THz radiation are induced by exciting the sample with a second optical pulse, phase locked with the first. We observe phase shifts in the emitted THz radiation of 330 fs for a change in the optical-pulse separation of only 1.33 fs
Book•
01 Dec 1993
TL;DR: In this paper, a theoretical modeling of the intersubband transitions in III-V semiconductor multiple quantum wells far-infrared materials based on InAs/GaInSb type II strained-layer superlattices infrared detectors using SiGe/Si quantum well structures for long-wavelength infrared detectors - the Hg/TeCaTe system.
Abstract: Introduction to long-wavelength infrared quantum detectors theoretical modeling of the intersubband transitions in III-V semiconductor multiple quantum wells far-infrared materials based on InAs/GaInSb type II strained-layer superlattices infrared detectors using SiGe/Si quantum well structures type III superlattices for long-wavelength infrared detectors - the Hg/TeCaTe system.
TL;DR: In this paper, a continuous-wave operation of ridge waveguide quantum well diode lasers in green/blue has been demonstrated at voltages as low as 4.4V in pseudomorphic separate confinement heterostructures, with output powers up to 10mW.
Abstract: Continuous-wave (CW) operation of ridge waveguide quantum well diode lasers in the green/blue has been demonstrated at voltages as low as 4.4V in ZnCdSe/ZnSSe/ZnMgSSe pseudomorphic separate confinement heterostructures, with output powers up to 10mW.
TL;DR: In this article, the authors experimentally observed an oscillating carrier capture time as a function of quantum well thickness, which correspond to a local capture time oscillating between 0.1 and 1.8 ps.
Abstract: We experimentally observed an oscillating carrier capture time as a function of quantum well thickness. The capture times were obtained in a separate confinement quantum well structure by subpicosecond rise time measurements of the quantum well luminescence as well as by pump-probe correlation measurements of the population decay in the barrier layer. Both experimental techniques yield an oscillating capture time between 3 and 20 ps, in excellent agreement with the theoretical predictions. In a classical picture, our results correspond to a local capture time oscillating between 0.1 and 1.8 ps. Furthermore, the dependence of the capture time on the excitation energy is analyzed and the time-dependent position of the quasi-Fermi-level in the barrier layer is tracked experimentally. We find that the carrier capture time is very sensitive to the detailed structure parameters as well as to the carrier distribution in the barrier. Carrier capture is found to be an ambipolar process in which the oscillations of the observed capture times are due to the quantum-mechanical oscillation of the electron wave-function overlap above the well. Finally, electron capture is demonstrated to be dominated by LO-phonon emission.
TL;DR: In this paper, a model for the spectral response of GaAs and AlxGa1−xAs p−n and p−i−n solar cells, with and without quantum wells, based on a standard solution of the minority-carrier equations, is presented.
Abstract: The quantum well solar cell is an alternative to more conventional multiband gap approaches to higher cell efficiency. Preliminary studies have shown that the insertion of a series of quantum wells into the depletion region of a GaAs/AlxGa1−xAs p‐i‐n solar cell can significantly enhance the cell’s short‐circuit current. We present here a model for the spectral response of GaAs and AlxGa1−xAs p‐n and p‐i‐n solar cells, with and without quantum wells, based on a standard solution of the minority‐carrier equations. Particular emphasis is placed on modeling the absorption coefficient of the AlxGa1−xAs and of the quantum wells. We find that our model can accurately predict the spectral response of a wide variety of cells: both conventional p‐n junctions in GaAs and AlxGa1−xAs, and various geometries of quantum well solar cell in AlxGa1−xAs/GaAs (x∼0.3). We discuss the strengths and weaknesses of the model and its underlying assumptions, and conclude by using the model to design p‐i‐n quantum well solar cells w...
TL;DR: By spin resolved photoemission, exchange-split spin-polarized electronic states in a nonmagnetic material deposited on a magnetic substrate are detected and spectral polarization and intensity at the Fermi level display a periodicity correlated with the oscillations of the long range coupling between magnetic films separated by Cu(100) layers.
Abstract: By spin resolved photoemission we have detected exchange-split spin-polarized electronic states in a nonmagnetic material deposited on a magnetic substrate. Epitaxial Cu overlayers on fcc Co(100) exhibit sp symmetry electronic states which are spin polarized by the confining magnetic interface. These spin-polarized states can be observed up to a film thickness of at least 10 atomic layers. The spectral polarization and intensity at the Fermi level display a periodicity correlated with the oscillations of the long range coupling between magnetic films separated by Cu(100) layers.
PARC1
TL;DR: In this article, the temperature dependence of threshold current and quantum efficiency for Ga/sub x/In/sub 1-x/P (x=0.4, 0.6; lambda =680, 633 nm) single 80-AA quantum-well lasers is compared and analyzed using a model for the electron leakage current.
Abstract: The temperature dependence of threshold current and quantum efficiency for Ga/sub x/In/sub 1-x/P (x=0.4, 0.6; lambda =680, 633 nm) single 80-AA quantum-well lasers is compared and analyzed using a model for the electron leakage current. This model fits the experimental data well, correctly describing the rapid increase in threshold and drop in quantum efficiency as temperature increases. Also, it indicates that the drift (rather than diffusion) component of the electron leakage current, is dominant, because of the poor p-type conductivity in AlGaInP. >
TL;DR: In this article, a new form of AlyGa1−yAs−GaAs•InxGa 1−xAs laser that is confined above and below the active region by an insulating low refractive index native oxide is demonstrated.
Abstract: A new form of AlyGa1−yAs‐GaAs‐InxGa1−xAs quantum well heterostructure (QWH) laser that is confined above and below the active region by an insulating low refractive index native oxide is demonstrated. The laser diodes are defined from a mesa edge by the selective lateral oxidation and anisotropic oxidation of high Al composition AlyGa1−yAs layers (y=0.85, 0.87) located above and below the QW and waveguide active region. This structure provides excellent current and optical confinement, resulting in continuous wave threshold currents of ∼8 mA and maximum output powers (uncoated laser) of 35 mW/ facet for a∼2.5 μm aperture.