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Showing papers on "Quantum well published in 1990"


Journal ArticleDOI
TL;DR: In this article, a selective conversion of high composition (AlAs)x(GaAs)1−x layers into dense transparent native oxide by reaction with H2O vapor (N2 carrier gas) at elevated temperatures (400 °C) is presented.
Abstract: Data are presented on the conversion (selective conversion) of high‐composition (AlAs)x(GaAs)1−x layers, e.g., in AlxGa1−xAs‐AlAs‐GaAs quantum well heterostructures and superlattices (SLs), into dense transparent native oxide by reaction with H2O vapor (N2 carrier gas) at elevated temperatures (400 °C). Hydrolyzation oxidation of a fine‐scale AlAs(LB)‐GaAs(Lz) SL (LB +Lz≲100 A), or random alloy AlxGa1−xAs (x≳0.7), is observed to proceed more slowly and uniformly than a coarse‐scale ‘‘alloy’’ such as an AlAs‐GaAs superlattice with LB + Lz≳200 A.

561 citations


Journal ArticleDOI
TL;DR: In this article, a GaAs quantum well infrared detector having a cutoff wavelength of λc=10.7 μm was used to achieve a blackbody detectivity of 1.0×1010 cm (Hz) 1/2/W at T=68 K, a temperature which is readily achievable with a cryogenic cooler.
Abstract: By increasing the quantum well barrier width, we have dramatically reduced the tunneling dark current by an order of magnitude and thereby significantly increased the blackbody detectivity D*BB. For a GaAs quantum well infrared detector having a cutoff wavelength of λc=10.7 μm, we have achieved D*BB =1.0×1010 cm (Hz)1/2/W at T=68 K, a temperature which is readily achievable with a cryogenic cooler.

346 citations


BookDOI
01 Jan 1990
TL;DR: In this article, the authors present a perspective on the evolution of quantum Semiconductor devices. But they do not discuss the theoretical foundations of these devices and do not provide a detailed analysis of them.
Abstract: 1. Introduction.- 1.1 A Perspective on the Evolution of Quantum Semiconductor Devices.- 1.2 Outline of the Book.- References.- 2. The Nature of Molecular Beam Epitaxy and Consequences for Quantum Microstructures.- 2.1 Dimensional Confinement and Device Concepts.- 2.2 Molecular Beam Epitaxy.- 2.2.1 Conceptual Picture.- 2.2.2 Reflection High Energy Electron Diffraction.- 2.2.3 Formation of Interfaces and Growth Interruption.- 2.3 The Surface Kinetic Processes and Computer Simulations of Growth.- 2.3.1 The CDRI Model.- 2.3.2 Growth Front Morphology.- 2.3.3 The CDRI Model and the Nature of GaAs/AlxGa1?xAs (100) Interfaces.- 2.4 Quantum Wells: Growth and Photoluminescence.- 2.5 Concluding Remarks.- 2.6 Recent Advances.- References.- 3. Nanolithography for Ultra-Small Structure Fabrication.- 3.1 Overview.- 3.2 Resolution Limits of Lithographic Processes.- 3.2.1 Lithography.- 3.2.2 Resolution Limits of Lithographic Methods.- 3.2.3 Photolithography and X-Ray Lithography.- 3.2.4 Ion Beams.- 3.2.5 Electron Beams.- 3.3 Pattern Transfer.- References.- 4. Theory of Resonant Tunnelling and Surface Superlattices.- 4.1 Tunnelling Probabilities.- 4.1.1 Single Barrier.- 4.1.2 Resonant Tunnelling Rates.- 4.2 Tunnelling Time.- 4.3 Pseudo-Device Calculations.- 4.3.1 The Wigner Function.- 4.3.2 Diode Response.- 4.4 Lateral Superlattices.- 4.4.1 Transport Effects.- 4.4.2 Bloch Oscillators.- 4.4.3 High Frequency Response.- References.- 5. The Investigation of Single and Double Barrier (Resonant Tunnelling) Heterostructures Using High Magnetic Fields.- 5.1 Background.- 5.2 LO Phonon Structure in the I(V) and C(V) Curves of Reverse-Biased Heterostructures.- 5.2.1 n-GaAs/(AlGa)As/GaAs Heterostructures.- 5.2.2 n-(InGa)As/InP/(InGa)As Heterostructures.- 5.2.3 Magnetocapacitance and Magnetic Freeze-out.- 5.3 Magnetotunnelling from the 2D Electron Gas in Accumulated (InGa)As/InP Structures Grown by MBE and MOCVD.- 5.4 Observation of Magnetoquantized Interface States by Electron Tunnelling in Single-Barrier n? (InGa)As/InP/n+ (InGa)As Heterostructures.- 5.5 Box Quantised States.- 5.6 Double Barrier Resonant Tunnelling Devices.- 5.6.1 Hybrid Magneto-electric States in Resonant Tunnelling Structures.- 5.6.2 Intrinsic Bistability in Resonant Tunnelling Devices.- 5.6.3 Magnetic Field Studies of Elastic Scattering and Optic Phonon Emission in Resonant Tunnelling Devices.- References.- 6. Microwave and Millimeter-Wave Resonant-Tunnelling Devices.- 6.1 Speed of Response.- 6.2 Resonant-Tunnelling Oscillators.- 6.3 Self-Oscillating Mixers.- 6.4 Resistive Multipliers.- 6.5 Variable Absolute Negative Conductance.- 6.6 Persistent Photoconductivity and a Resonant-Tunnelling Transistor.- 6.7 A Look at Resonant-Tunnelling Theory.- 6.7.1 Stationary-State Calculation.- 6.7.2 Temporal Behavior.- 6.7.3 Scattering.- 6.8 Concluding Remarks.- Note Added in Proof.- List of Symbols.- References.- 7. Resonant Tunnelling and Superlattice Devices: Physics and Circuits.- 7.1 Resonant Tunnelling Through Double Barriers and Superlattices.- 7.1.1 The Origin of Negative Differential Resistance.- 7.1.2 Coherent (Fabry-Perot-Type) Resonant Tunnelling.- 7.1.3 The Role of Scattering: Sequential Resonant Tunnelling Through Double Barriers and Superlattices.- 7.1.4 Ga0.47In0.53As/Al0.48In0.52As Resonant Tunnelling Diodes.- 7.1.5 Resonant Tunnelling Through Parabolic Quantum Wells.- 7.1.6 Resonant Tunnelling Electron Spectroscopy.- 7.2 Application of Resonant Tunnelling: Transistors and Circuits.- 7.2.1 Integration of Resonant Tunnelling Diodes and Their Circuit Applications.- a) Horizontal Integration of RT Diodes.- b) Vertical Integration of RT Diodes.- 7.2.2 Resonant Tunnelling Bipolar Transistors.- a) Circuit Applications of RTBTs.- b) Resonant Tunnelling Bipolar Transistors Operating at Room Temperature.- c) Alternative Designs of RTBTs.- d) RTBT with Multiple Peak Characteristics.- 7.2.3 Resonant Tunnelling Unipolar Transistors.- a) Resonant Tunnelling Gate Field Effect Transistor.- b) Quantum Wire Transistor.- c) The Gated Quantum Well Resonant Tunnelling Transistor.- References.- 8. Resonant-Tunnelling Hot Electron Transistors (RHET).- 8.1 RHET Operation.- 8.2 RHET Technology Using GaAs/AlGaAs Heterostructures.- 8.3 InGaAs-Based Material Evaluation.- 8.4 RHET Technology Using InGaAs-Based Materials.- 8.5 Theoretical Analyses of RHET Performance.- 8.6 Summary.- References.- 9. Ballistic Electron Transport in Hot Electron Transistors.- 9.1 Ballistic Transport.- 9.1.1 The Search for Ballistic Transport.- 9.1.2 Properties of GaAs.- 9.2 Hot Electron Transistors.- 9.2.1 Principles of Operation.- 9.2.2 Some History.- 9.3 Hot Electron Injectors.- 9.3.1 What is a Hot Electron Injector?.- 9.3.2 The Thermionic Injector.- 9.3.3 The Tunnel Injector.- 9.4 Energy Spectroscopy.- 9.4.1 Spectroscopy Defined.- 9.4.2 Band Pass Spectrometer.- 9.4.3 High Pass Spectrometer.- 9.4.4 Energy Resolution of the Square Type Barrier.- 9.4.5 Observation of Quasi Ballistic and Ballistic Electron Transport in GaAs.- 9.4.6 Observation of Ballistic Hole Transport in GaAs.- 9.5 Electron Coherent Effects in the THETA Device.- 9.5.1 Size Quantization Effects.- 9.5.2 Classical and Self-Consistent Well Potential.- 9.5.3 Tunnelling into a Well.- 9.5.4 Nonparabolicity Effects, Real and Resonant States.- 9.5.5 Interference Effects of Ballistic Holes.- 9.6 Transfer to the L Satellite Valleys.- 9.6.1 Spectroscopic Observations.- 9.6.2 Verification of the Intervalley Transfer.- 9.7 The THETA as a Practical Device.- 9.7.1 Gain Considerations.- 9.7.2 Speed Considerations.- 9.7.3 Final Comments.- References.- 10. Quantum Interference Devices.- 10.1 Background.- 10.2 Two-Port Quantum Devices.- 10.2.1 Conductance Formula.- 10.2.2 Quantum Interference Transistor.- 10.3 Multiport Quantum Devices.- 10.3.1 Conductance Formula.- 10.3.2 Quantum Reflection Transistor.- 10.3.3 Quantum Networks.- Appendix: Aharonov - Bohm Phase-shift in an Electric or Magnetic Field.- References.- Additional References.- 11. Carrier Confinement to One and Zero Degrees of Freedom.- 11.1 Experimental Methods.- 11.2 Discussion of Experimental Results.- 11.3 Conclusions.- References.- 12. Quantum Effects in Quasi-One-Dimensional MOSFETs.- 12.1 Background.- 12.2 MOSFET Length Scales.- 12.3 Special MOSFET Geometries.- 12.4 Strictly 1D Transport.- 12.4.1 Localization and Resonant Tunnelling.- 12.4.2 Hopping Transport.- 12.5 Multichannel Transport (Particle in a Box?).- 12.6 Averaged Quantum Diffusion.- 12.6.1 Weak Localization.- 12.6.2 Electron-Electron Interactions.- 12.7 Mesoscopic Quantum Diffusion (Universal Conductance Fluctuations).- 12.7.1 Universal Conductance Fluctuations at Scale Lo.- 12.7.2 Self-Averaging of Conductance Fluctuations at Larger Probe Spacings.- 12.7.3 Nonlocal Response of Conductance Fluctuations at Shorter Probe Spacings.- 12.7.4 Comprehensive Comparison Between Theory and Experiment.- 12.7.5 Internal Asymmetries of Mesoscopic Devices.- 12.8 Effect of One Scatterer.- 12.8.1 Interface Traps.- 12.8.2 Quantum Effect of One Scatterer.- 12.9 Conclusion.- References.

296 citations


Journal ArticleDOI
TL;DR: This poster presents a probabilistic simulation of the response of the immune system to a drug-like substance and shows clear patterns of action towards certain immune-like responses.
Abstract: Binding energies of excitons in quantum wells are calculated including valence-band mixing and also other important effects, namely Coulomb coupling between excitons belonging to different subbands (which is predominantly with the exciton continuum), nonparabolicity of the bulk conduction band, and the difference in dielectric constants between well and barrier materials. All these effects are found to be of a comparable size, tend to increase the binding energies, and taken together result in very high binding energies, particularly in narrow GaAs/AlAs quantum wells. Binding energies can be even higher than the two-dimensional limit of four times the bulk Rydberg. Theoretical results agree within a few tenths of a milli-electron-volt with available photoluminescence excitation experiments. Valence-band mixing gives a finite oscillator strength to some excitons not in s states, but does not change the selection rules based on parity. Calculated oscillator strengths of the ground-state heavy- and light-hole excitons are found to be in good agreement with absorption and reflectivity experiments.

265 citations


Journal ArticleDOI
TL;DR: In this paper, a new formalism for determining energy eigenstates of spherical quantum dots and cylindrical quantum wires in the multiple-band envelope function approximation is described, based upon a reformulation of the K⋅P theory in a basis of eigen states of total angular momentum.
Abstract: We describe a new formalism for determining energy eigenstates of spherical quantum dots and cylindrical quantum wires in the multiple-band envelope-function approximation. The technique is based upon a reformulation of the K⋅P theory in a basis of eigenstates of total angular momentum. Stationary states are formed by mixing bulk energy eigenvectors and imposing matching conditions across the heterostructure interface, yielding dispersion relations for eigenenergies in quantum wires and quantum dots. The bound states are studied for the conduction band and the coupled light and heavy holes as a function of radius for the GaAs/AlxGa1-xAs quantum dot. Conduction-band–valence-band coupling is shown to be critical in a "type-II" InAs/GaSb quantum dot, which is studied here for the first time. Quantum-wire valence-subband dispersion and effective masses are determined for GaAs/AlxGa1-xAs wires of several radii. The masses are found to be independent of wire radius in an infinite-well model, but strongly dependent on wire radius for a finite well, in which the effective mass of the highest-energy valence subband is as low as 0.16m0. Implications of the band-coupling effects on optical matrix elements in quantum wires and dots are discussed.

250 citations


Journal ArticleDOI
TL;DR: The optical properties of the quantum dots are computed, and it is shown that the Coulomb interaction significantly influences the allowed dipole transitions, causing increasing two-pair absorption on the high-energy side of the decreasing one- Pair absorption.
Abstract: The influence of the Coulomb interaction on one and two electron-hole-pair excitations in semiconductor quantum dots is analyzed. Using a numerical matrix-diagonalization scheme, the energy eigenvalues and the eigenfunctions of the relevant states are computed. Significant deviations from the strong-confinement approximation are observed. It is shown that the biexciton binding energy increases with decreasing dot size. This result is verified using third-order perturbation theory for small quantum dots. The optical properties of the quantum dots are computed, and it is shown that the Coulomb interaction significantly influences the allowed dipole transitions, causing increasing two-pair absorption on the high-energy side of the decreasing one-pair absorption. Surface-polarization effects are studied for quantum dots embedded in another dielectric medium.

239 citations


Journal ArticleDOI
TL;DR: With far-infrared spectroscopy, coupling between electron quantum dots becomes visible in the electronic excitation spectrum and gated GaAs-AlGaAs quantum wells that enable field-effect tuning of the coupling between adjacent dots are employed.
Abstract: With far-infrared spectroscopy, coupling between electron quantum dots becomes visible in the electronic excitation spectrum. We employ gated GaAs-AlGaAs quantum wells that enable field-effect tuning of the coupling between adjacent dots. For noninteracting quantum dots in a magnetic field we observe the characteristic edge- and bulk-mode spectrum.. The coupling of dots is reflected by a branching of the bulk mode into a cyclotron-resonance-like and a magnetoplasmonlike mode and a splitting of the edge mode. The latter is caused by formation of new edge orbits embracing two adjacent dots.

224 citations


Journal ArticleDOI
TL;DR: Application de the resonance magnetique detectee optiquement a l'etude des excitons dans les puits quantiques observe deux classes d'excitons, chacun ayant une symetrie inferieure a la sy metrie du groupe ponctuel D 2d anticipee pour les exciton dans the puitsquantiques.
Abstract: Optically detected magnetic resonance in zero field as well as in a finite magnetic field has been used to study the excitons in type-II GaAs/AlAs quantum wells. The spectra are analyzed using the appropriate spin Hamiltonian for the quasi-two-dimensional indirect excitons. The electron-hole exchange interaction and the g factors for the electron and hole are obtained for several thicknesses of the GaAs and AlAs layers. Good agreement exists between the trend in the exchange interaction and the effective-mass theory of Rejaei Salmassi and Bauer. The anisotropy of the electron g factor is in accordance with a lifting of the threefold degeneracy of the AlAs X conduction-band minimum by the quantum-well potential giving the ${\mathit{X}}_{\mathit{z}}$ valley the lowest energy in the thin-layer quantum wells studied. The effective heavy-hole g value of \ensuremath{\sim}2.5 is much smaller than in the bulk and depends on the GaAs well thickness. This is probably a consequence of the valence-band mixing in quantum-well structures. Two classes of excitons are observed, each with a symmetry that is lower than the anticipated ${\mathit{D}}_{2\mathit{d}}$ point-group symmetry for excitons in quantum wells. The actual symmetry of the type-II excitons and the width of the exciton resonances are related to the microscopic structure of the GaAs/AlAs interface.

195 citations


Journal ArticleDOI
TL;DR: In this paper, vertical-cavity surface-emitting lasers fabricated utilizing a self-aligned process to provide planarized contacts are discussed, and a single 80-AA In/sub 0.2/Ga/sub 1.8/As strained quantum well was used in the active region.
Abstract: Vertical-cavity surface-emitting lasers fabricated utilizing a self-aligned process to provide planarized contacts are discussed. A single 80-AA In/sub 0.2/Ga/sub 0.8/As strained quantum well was used in the active region. Emission was at 963 nm. Threshold currents under continuous-wave room temperature operation of 1.1 mA, at 4.0-V bias, were measured for numerous 12- mu m*12- mu m devices. Corresponding threshold current densities were 800 A/cm/sup 2/ (600 A/cm/sup 2/ for broad area devices). These are the lowest figures yet reported for this type of device. It was found that grading of the mirror had a marked effect on mirror resistance. >

187 citations


Journal ArticleDOI
TL;DR: In this article, the photoluminescence intensity increases in the cavity axis direction, and the spontaneous emission lifetime is experimentally found to decrease with an on-resonance cavity structure.
Abstract: Enhanced spontaneous emission has been observed with wavelength‐sized monolithic Fabry–Perot cavities containing GaAs quantum wells. With an on‐resonance cavity structure, the photoluminescence intensity increases in the cavity axis direction, and the spontaneous emission lifetime is experimentally found to decrease.

184 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reported the first direct demonstration of a strain-generated built-in electric field in a (111) oriented strained-layer heterostructure, where the misfit strain in a lattice mismatched quantum well was exploited to generate a longitudinal electric field via the piezoelectric effect.
Abstract: We report the first direct demonstration of a strain‐generated built‐in electric field in a (111) oriented strained‐layer heterostructure. We present a model which describes the accommodation of the misfit strain in a lattice‐mismatched quantum well, and the resulting generation of a longitudinal electric field via the piezoelectric effect. On a (111)B GaAs substrate, we grew the quantum well in the intrinsic region of a p‐i‐n diode such that the strain‐generated electric field in the quantum well opposes the weaker built‐in electric field of the diode. Under reverse bias operation, photoconductivity measurements show a quadratic blue shift of the quantum well electroabsorption peaks, in contrast to the red shifts normally observed in the quantum‐confined Stark effect. The measured blue shifts demonstrate an electric field strength of 1.7×105 V/cm, which agrees with theory to within the accuracy of the measured sample characteristics.

Journal ArticleDOI
TL;DR: It is confirmed that a perfect WPQW absorbs light only at the bare harmonic-oscillator frequency, and it is shown that the effects of small imperfections of the types considered on the absorption spectrum are twofold: a shift in the location of the main peak and the appearance of new peaks nearby.
Abstract: The effects of possible imperfections on the infrared optical absorption and on the charge-density profile of wide parabolic quantum wells (WPQW's) are studied. We consider effects that can arise from the finite width of WPQW's, from the existence of a quartic component in the confining potential, and from the existence of a region of flat potential in the center of the well. Within the local-density approximation, we confirm that a perfect WPQW absorbs light only at the bare harmonic-oscillator frequency, and show that the effects of small imperfections of the types considered on the absorption spectrum are twofold: a shift in the location of the main peak and the appearance of new peaks nearby.

Journal ArticleDOI
TL;DR: In this paper, a single quantum well diode InGaAs/AlGaAs single-well diode laser emitting at 1.02 μm has been fabricated from structures grown by organometallic vapor phase epitaxy.
Abstract: Graded‐index separate‐confinement heterostructure InGaAs/AlGaAs single quantum well diode lasers emitting at 1.02 μm have been fabricated from structures grown by organometallic vapor phase epitaxy. Under pulsed operation, threshold current densities as low as 65 A/cm2, the lowest reported for InGaAs/AsGaAs lasers, have been obtained for a cavity length L of 1500 μm. Differential quantum efficiencies as high as 90% have been obtained for L=300 μm. Output powers as high as 1.6 W per facet and power conversion efficiencies as high as 47% have been obtained for continuous operation of uncoated lasers with L=1000 μm.

Journal ArticleDOI
TL;DR: The observation of quantum beats in the decay of the coherent polarization of intrinsic excitations in GaAs/GaAlAs quantum wells is reported, which arises from interference of excitons with slightly different quantum confinement energy due to well-width fluctuations.
Abstract: We report the observation of quantum beats in the decay of the coherent polarization of intrinsic excitations in GaAs/GaAlAs quantum wells. The beating arises from interference of excitons with slightly different quantum confinement energy due to well width fluctuations.

Journal ArticleDOI
TL;DR: Calcul des vitesses de diffusion pour un electron interagissant avec des phonons optiques dans un puits quantique semiconducteur, base on une approche de dynamique reticulaire microscopique pour les phonons.
Abstract: We calculate scattering rates for an electron interacting with polar optical phonons in a semiconductor quantum well based on a microscopic lattice-dynamics approach for the phonons. We employ an analytic approximation to lattice-dynamics results given by Huang and Zhu for quantum-well phonons. The resulting electron relaxation rates are compared with the rates obtained by employing ``slab'' and ``guided'' phonon modes which were used in previous studies. The intrasubband and intersubband electron relaxation rates are given as functions of quantum-well width, and the relative contributions of the confined and the interface modes are discussed for the three different phonon models.

Journal ArticleDOI
TL;DR: In this paper, a new technique for creating independent ohmic contacts to closely spaced two-dimensional electron systems in double quantum well (DQW) structures is described, which results in low-resistance contacts which can be electrostatically switched between the two-conducting layers.
Abstract: A new technique for creating independent ohmic contacts to closely spaced two‐dimensional electron systems in double quantum well (DQW) structures is described. Without use of shallow diffusion or precisely controlled etching methods, the present technique results in low‐resistance contacts which can be electrostatically switched between the two‐conducting layers. The method is demonstrated with a DQW consisting of two 200 A GaAs quantum wells separated by a 175 A AlGaAs barrier. A wide variety of experiments on Coulomb and tunnel‐coupled 2D electron systems is now accessible.

Journal ArticleDOI
TL;DR: Theoretical investigation of the electronic properties of a quasi-one-dimensional electron system at very low temperature for a cylindrical quantum wire and analytical results are in good agreement with the exact results for the model.
Abstract: We present a theoretical investigation of the electronic properties of a quasi-one-dimensional electron system at very low temperature. For a cylindrical quantum wire the electron-impurity interaction and the electron-electron interaction is calculated for a two-subband model. Our analytical results for the electron-impurity and the electron-electron interaction are in good agreement with the exact results for our model. Analytical results for the band bending due to the filling of the lowest subband are evaluated. Within our analytical results we discuss various aspects of the electronic properties of the semiconductor quantum wire: screening (intrasubband and intersubband plasmons), shallow impurity states (screened and unscreened), and mobility (ionized-impurity scattering and interface-roughness scattering). Analytical expressions are given for the dispersion of plasmons, the binding energies of shallow impurities, and the mobility. Our results on intersubband plasmons are compared with experiments.

Journal ArticleDOI
TL;DR: In this paper, the authors presented the first detailed theoretical study of gain in strained InGaAs/AlGaAs quantum wells, taking into account the complex nature of the valence subband structure, which must be included in any realistic model.
Abstract: In this letter, we present the first detailed theoretical study of gain in strained InGaAs/AlGaAs quantum wells, taking into account the complex nature of the valence‐subband structure, which must be included in any realistic model. We first compare the material gain as a function of carrier and radiative current density for a strained and unstrained quantum well. We then present calculations of theoretical differential gain, carrier density, and radiative current density at transparency as a function of indium mole fraction in the well.

Journal ArticleDOI
TL;DR: In this article, the conduction and valence-band offsets for GaAs/Ga0.51In0.49P quantum wells were independently estimated by measuring the capacitance transient resulting from thermal emission of carriers from the respective wells.
Abstract: We have independently estimated the conduction‐ and valence‐band offsets ΔEc and ΔEv in GaAs/Ga0.51In0.49P quantum wells by measuring the capacitance transient resulting from thermal emission of carriers from the respective wells. The heterostructure samples were grown by low‐pressure metalorganic chemical vapor deposition. The band offsets are extrapolated from the emission activation energies with appropriate corrections. The estimated values of ΔEc and ΔEv are 0.198 and 0.285 eV, respectively.

Journal ArticleDOI
TL;DR: In this article, a tunable infrared modulator and/or switch using intersubband Stark shift in a step quantum well is discussed, which utilizes the inter-band absorption and the large change of separation between energy levels under an applied electric field.
Abstract: A tunable infrared modulator and/or switch using intersubband Stark shift in a step quantum well is discussed. The device utilizes the intersubband absorption and the large change of separation between energy levels in the step quantum well under an applied electric field. The incident infrared beam on the device is either absorbed or transmitted depending on the energy separation of the levels, and thus the modulation can be achieved by adjusting the energy levels with an applied electric field. The extremely short lifetime of the intersubband transition makes this modulator suitable for application in high-speed long-wavelength optical communications. >

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz and found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz.
Abstract: The possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz was investigated theoretically and experimentally. It is found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz. At these high frequencies, only a few modes are locked and the output usually takes the form of a deep sinusoidal modulation which is synchronized in phase with the externally applied modulation at the intermodal heat frequency. This can be regarded for practical purposes as a highly efficient means of directly modulating an optical carrier over a narrow band at millimeter wave frequencies. Both active and passive mode locking are theoretically possible. >

Journal ArticleDOI
TL;DR: In this article, a semi-insulating multiple quantum well was proposed to combine the holographic properties of the photorefractive effect with the large resonant optical nonlinearities of quantum-confined excitons.
Abstract: We use semi-insulating multiple quantum wells to combine the holographic properties of the photorefractive effect with the large resonant optical nonlinearities of quantum-confined excitons. GaAs–AlGaAs multiple-quantum-well structures are made semi-insulating by proton implantation. The implant damage produces defects that are available to trap and store charge during transient holographic recording by means of coherent excitation. The advantages of charge storage and resonant optical nonlinearity combine to produce new optical devices with large sensitivities. The potential use of these devices for image processing is demonstrated by using the Franz–Keldysh effect in four-wave mixing at wavelengths near 830 nm.

Journal ArticleDOI
TL;DR: In this paper, the first time room-temperature, continuous-wave operation of individual vertical-cavity laser diodes with submilliampere threshold currents was reported.
Abstract: We report for the first time room‐temperature, continuous‐wave operation of individual vertical‐cavity laser diodes with submilliampere threshold currents. A single quantum well active region emitting at 979 nm surrounded by GaAs/AlAs Bragg reflector mirrors was used. Threshold currents were as low as 0.7 mA. A record low linewidth‐power product of 5 MHz mW and a linewidth as narrow as 85 MHz was measured. High yield and good uniformity were demonstrated.

Journal ArticleDOI
Yong-Hee Lee1, B. Tell1, K.F. Brown-Goebeler1, Jl Jewell1, Jv Hove 
TL;DR: In this paper, the authors achieved room-temperature CW and pulsed lasing of top-surface-emitting, vertical-cavity, self-aligned, GaAs quantum-well lasers at 845 nm.
Abstract: Room-temperature CW and pulsed lasing of top-surface-emitting, vertical-cavity, self-aligned, GaAs quantum-well lasers is achieved at ~845 nm. The active gain medium is four 100-A-thick GaAs quantum wells. The whole structure is grown by molecular beam epitaxy. Deep H+-ion implantation followed by annealing is used to control a vertical profile of resistivity for an efficient current injection at the active region. The threshold current is 2.2 mA for CW and pulsed operation using 10-jam diameter lasers. Differential quantum efficiency is about 20%. Minimum threshold current density per quantum well of 360 A/cm2 is obtained. Maximum CW output power better than 1.5 mW is obtained.

Journal ArticleDOI
TL;DR: In this article, the authors reported the determination of Auger recombination coefficients in bulk and quantum well InGaAs by time-resolved luminescence measurements, and they found that the Auger coefficient decreases slightly with decreasing well width.
Abstract: We report the determination of Auger recombination coefficients in bulk and quantum well InGaAs by time‐resolved luminescence measurements. In bulk InGaAs the coefficient is C=3.2×10−28 cm6/s and has the temperature dependence of the valence‐band Auger effect involving the split‐off valence band. In 11 nm quantum well InGaAs we find C=0.9×10−28 cm6/s, independent of temperature. The Auger coefficient decreases slightly with decreasing well width.

Journal ArticleDOI
TL;DR: In this paper, a single quantum well material using electron-beam lithography and SiCl4 dry etching was used to construct a ring laser with a threshold current of 24 mA, which is suitable for monolithic integration in optoelectronic circuits.
Abstract: Semiconductor ring lasers have been fabricated in single quantum well material using electron-beam lithography and SiCl4 dry etching. CW operation has been achieved in 84 μm diameter rings at a threshold current of 24 mA. This low value makes the structure very suitable for monolithic integration in optoelectronic circuits.

Journal ArticleDOI
TL;DR: In this paper, it was shown that photoluminescence in InGaAs/GaAs strained-layer quantum wells is strongly quenched by temperatures above 10−100 K, depending on the well width, and thermal activation of electronhole pairs from the wells into the GaAs barriers, followed by nonradiative recombination through a loss mechanism in bulk GaAs.
Abstract: Photoluminescence in InGaAs/GaAs strained‐layer quantum wells is strongly quenched by temperatures above 10–100 K, depending on the well width. Analysis of this dependence shows that the quenching mechanism is thermal activation of electron‐hole pairs from the wells into the GaAs barriers, followed by nonradiative recombination through a loss mechanism in bulk GaAs. The addition of Al to the barriers to improve confinement eliminates loss through this route but introduces another loss mechanism, characterized by an activation energy independent of well width and with a smaller pre‐exponential factor.

Journal ArticleDOI
Kazuhisa Uomi1
TL;DR: In this article, a number of important parameters, such as gain, modulation response and threshold current in modulation-doped multi-quantum-well (MD-MQW) lasers are theoretically investigated.
Abstract: A number of important parameters, such as gain, modulation response and threshold current in modulation-doped multi-quantum-well (MD-MQW) lasers are theoretically investigated. The analytical results indicate that the relaxation oscillation frequency of p-type MD-MQW lasers is enhanced by a factor of 4 compared with DH lasers, and that the linewidth enhancement factor of p-type MD-MQW lasers is reduced to 1/4 that of undoped MQW lasers. The threshold current density of n-type MD-MQW lasers is reduced to 1/2~1/4 that of undoped MQW lasers. The improvements in these properties basically result from the unsatisfied charge neutrality due to the modulation doped effect and from asymmetry in density of states between conduction band and valence bands in III-V materials.

Journal ArticleDOI
TL;DR: In this paper, self-consistent solutions of the Schrodinger and Poisson equations are used to find the electron states in GaAs/AlGaAs quantum well wires.
Abstract: Two‐dimensional, self‐consistent solutions of the Schrodinger and Poisson equations are used to find the electron states in GaAs/AlGaAs quantum well wires. Both deep and shallow mesa structures are simulated. Our results show that while these structures are capable of providing the single occupied subband and wide energy separations needed for a true quantum wire, the process tolerances allowed are very small, on the order of 200 A of width variation. Cutoff widths calculated are 1000 A for the shallow mesa and 2100 A for the deep mesa. The agreement with experimental results is good for the shallow mesa, but poor for the deep mesa. This suggests additional process‐induced sidewall depletion mechanisms contributing to the cutoff of the deep mesa structures.

Journal ArticleDOI
Abstract: The effects of valence band mixing on the nonlinear gains of quantum-well lasers are studied theoretically for the first time. The analysis is based on the multiband effective-mass theory and the density matrix formalism with intraband relaxation taken into account. The gain and the gain-suppression coefficient of a quantum-well laser are calculated from the complex optical susceptibility obtained by the density matrix formulation with the theoretical dipole moments obtained from the multiband effective-mass theory. The calculated gain spectrum shows that there are differences (both in peak amplitude and spectral shape) between this model with valence band mixing and the conventional parabolic band model. The shape of the gain spectrum calculated by the new model becomes more symmetric due to intraband relaxation together with nonparabolic energy dispersions. Optical intensity in the GaAs active region is estimated by solving rate equations for the stationary states with nonlinear gain suppression. >