Showing papers on "Quantum well published in 1986"
TL;DR: In this article, the electronic dipole moment and its polarization dependence are analyzed, and it is shown that the gain becomes maximum when the electric field of light is parallel to the longest side of the quantum box.
Abstract: Gain and threshold current density are analyzed for quantum-box lasers where electrons are confined in quantum well three-dimensionally, based on the density-matrix theory of semiconductor lasers with relaxation broadening. The electronic dipole moment and its polarization dependence are first analyzed, and it is shown that the gain becomes maximum when the electric field of light is parallel to the longest side of the quantum box. Calculated gain is about 10 times that of bulk crystal for 100 A × 100 A × 100 A GaAs/Ga 0.8 Al 0.2 As quantum box, and 15 times for Ga 0.47 In 0.53 As/InP quantum box with the same size, respectively. The threshold current density are 45 A/cm2and 62 A/cm2for GRINSCH GaAs/(Ga 0.8 Al 0.2 As-Ga 0.4 Al 0.6 As) and Ga 0.47 In 0.53 As/(Ga 0.28 In 0.72 As 0.6 P 0.4 -InP), respectively, where for the GaInAs/ GaInAsP/InP system the intervalence band absorption and nonradiative recombinations have been assumed to be the same as those obtained for bulk crystals experimentally. These results show the possibility of remarkable reduction in the laser threshold by the quantum-box structures.
1,020 citations
TL;DR: In this article, the effects of feedback on the spectra of 1.5-μm DFB lasers from feedback power ratios as low as -80 dB up to -8 dB were measured.
Abstract: We have measured the effects of feedback on the spectra of 1.5-μm DFB lasers from feedback power ratios as low as -80 dB up to -8 dB. Five distinct regimes of effects are observed with well defined transitions between them. The dependence of these effects on the distance to the reflection is also investigated.
729 citations
TL;DR: In this article, a simple expression for the low field mobility in the miniband conduction regime is derived; localization effects, hopping conduction, and effective mass filtering are discussed.
Abstract: New results on the physics of tunneling in quantum well heterostructures and its device applications are discussed. Following a general review of the field in the Introduction, in the second section resonant tunneling through double barriers is investigated. Recent conflicting interpretations of this effect in terms of a Fabry-Perot mechanism or sequential tunneling are reconciled via an analysis of scattering. It is shown that the ratio of the intrinsic resonance width to the total scattering width (collision broadening) determines which of the two mechanisms controls resonant tunneling. The role of symmetry is quantitatively analyzed and two recently proposed resonant tunneling transistor structures are discussed. The third section deals with perpendicular transport in superlattices. A simple expression for the low field mobility in the miniband conduction regime is derived; localization effects, hopping conduction, and effective mass filtering are discussed. In the following section, experimental results on tunneling superlattice photoconductors based on effective mass filtering are presented. In the fifth section, negative differential resistance resulting from localization in a high electric field is discussed. In the last section, the observation of sequential resonant tunneling in superlattices is reported. We point out a remarkable analogy between this phenomenon and paramagnetic spin resonance. New tunable infrared semiconductor lasers and wavelength selective detectors based on this effect are discussed.
555 citations
TL;DR: In this article, the authors discuss a number of theoretical and experimental issues in quantum well lasers with emphasis on the basic behavior of the gain, the field spectrum, and the modulation dynamics and reveal that the use of quantum well structures results in improvement of these properties and brings several new concepts to optical semiconductor devices.
Abstract: We discuss a number of theoretical and experimental issues in quantum well lasers with emphasis on the basic behavior of the gain, the field spectrum, and the modulation dynamics It is revealed that the use of quantum well structures results in improvement of these properties and brings several new concepts to optical semiconductor devices
534 citations
TL;DR: In this paper, it is shown that by using a strained-layer superlattice to form the active region of a quantum-well laser, the threshold current can be reduced and Auger recombination and inter-valence band absorption can be effectively eliminated.
Abstract: It is shown that by using a strained-layer superlattice to form the active region of a quantum-well laser the threshold current can be reduced and Auger recombination and inter-valence band absorption can be effectively eliminated. The band-structure requirements are discussed generally and might be achieved by alternative methods.
527 citations
TL;DR: In this article, a carrier confinement to one and zero degrees of freedom has been achieved in artificial quantum well wires and boxes fabricated in the GaAs•GaAlAs system, which is attributed to transitions arising from ground and excited levels of electrons within these low dimensional structures.
Abstract: Carrier confinement to one and zero degrees of freedom has been achieved in artificial quantum well wires and boxes fabricated in the GaAs‐GaAlAs system. Low‐temperature cathodoluminescence measurements show new luminescence lines attributed to transitions arising from ground and excited levels of electrons within these low dimensional structures.
403 citations
TL;DR: In this paper, the electronic energy levels of semiconductor heterostructures within the envelope function scheme were described and the Coulombic bound states in heterostructure (impurities, excitons) were discussed, and the effect of a static electric field on the carrier and exciton energy levels in semiconductor quantum wells.
Abstract: This paper describes the electronic energy levels of semiconductor heterostructures within the envelope function scheme. Quantum well and superlattice electronic states are calculated and discussed, especially the in-plane dispersion relations. The Coulombic bound states in heterostructures (impurities, excitons) are then discussed. Finally, we present a brief overview of the effect of a static electric field on the carrier and exciton energy levels in semiconductor quantum wells.
397 citations
TL;DR: In this paper, GaAs and AlAs were used for growing high quality GaAs/AlAs layers at very low temperatures by alternately supplying Ga or Al atoms and As4 molecules to the GaAs substrate.
Abstract: When Ga or Al atoms are evaporated on a clean GaAs surface in an As-free atmosphere, they are quite mobile and migrate very rapidly along the surface even at low temperatures. This characteristic are utilized for growing high-quality GaAs and AlAs layers at very low temperatures by alternately supplying Ga or Al atoms and As4 molecules to the GaAs substrate. Applying this method, GaAs layers and AlAs–GaAs quantum well structures with reasonable photoluminescence characteristics are grown at 200°C and 300°C, respectively.
331 citations
TL;DR: In this paper, the authors evaluate the interband optical absorption of a semiconductor quantum well in the presence of a uniform electric field perpendicular to the layer and neglecting excitonic effects, and they show that this formally becomes the Franz-Keldysh effect in the limit of an infinitely thick layer.
Abstract: We evaluate the interband optical absorption of a semiconductor quantum well in the presence of a uniform electric field perpendicular to the layer and neglecting excitonic effects. We show that this formally becomes the Franz-Keldysh effect in the limit of an infinitely thick layer. When the potential drop across the layer is small compared to the confinement energy we obtain behavior qualitatively different from the bulk Franz-Keldysh effect and we explain this in terms of a quantum-confined Franz-Keldysh effect; with increasing field we demonstrate numerically for a GaAs-like semiconductor that we recover Franz-Keldysh-like behavior, once the originally ``forbidden'' quantum-well transitions become strong. Our discussion gives an alternative physical picture for the Franz-Keldysh effect, including a simple explanation of the Franz-Keldysh oscillations.
299 citations
TL;DR: In this paper, the authors summarize the electric field dependence of absorption and luminescence in quantum wells for fields perpendicular to the layers, present extended discussion of electroabsorption spectra and devices in waveguide samples, and derive sum rules for electro absorption.
Abstract: We summarize the electric-field dependence of absorption and luminescence in quantum wells for fields perpendicular to the layers, present extended discussion of electroabsorption spectra and devices in waveguide samples, and derive sum rules for electroabsorption. Optical bistability, self-linearized modulation, and optical level shifting are demonstrated in self-electrooptic effect device configurations, with good modulation contrast and polarization-dependent properties. The electroabsorption spectra enable quantitative comparison of theory and experiment for absorption strengths in quantum wells with field. The sum rules enable excitonic effects to be included in the comparison, and good agreement is seen. One sum rule is also more generally applicable to electroabsorption in semiconductors.
271 citations
TL;DR: In this paper, the photoluminescence and photoexcitation spectra of ultrasmall structures, referred to as quantum ribbons and quantum disks, were studied and compared.
Abstract: We have studied the photoluminescence and photoexcitation spectra of ultrasmall structures, of approximately 500 A in dimension, which we refer to as quantum ribbons and quantum disks. These are fabricated from GaAs‐AlGaAs quantum wells grown by molecular beam epitaxy and patterned by electron beam lithography. Contrary to our expectation, photoluminescence from these structures is extremely efficient. The excitation spectra of the two types of small structures differ greatly from each other and from that of the as‐grown quantum wells. These differences may be a result of the confinement of the carriers in these small structures.
TL;DR: The first reported experimental observation of an extremely fast shift of the n = 1 exciton transition energy in GaAs quantum-well heterostructures is described and interpreted in terms of an optical Stark effect.
Abstract: We describe the first reported experimental observation of an extremely fast shift of the n = 1 exciton transition energy in GaAs quantum-well heterostructures. The shift is produced by optical pumping below the band gap and is not associated with a carrier or exciton population. We interpret the shift in terms of an optical Stark effect. We present a model for the Stark effect on the ground-state exciton in quantum wells and find good agreement between the predictions of the model and our experimental results.
TL;DR: In this article, negative conductance regions in the low-temperature photocurrent-voltage characteristic of tight-binding multiquantum well (35 periods) 1μm-thick Al0.48 In0.52As/ Ga0.47 In 0.53As superlattices were observed.
Abstract: We report the observation of two negative conductance regions in the low‐temperature photocurrent‐voltage characteristic of tight‐binding multiquantum well (35 periods) 1‐μm‐thick Al0.48 In0.52As/ Ga0.47 In0.53As superlattices grown by molecular beam epitaxy. The two peaks occur at voltages corresponding to a potential energy drop across the superlattice period equal to the energy differences between the first two excited states and the ground state of the quantum wells. This provides direct evidence of sequential resonant tunneling between the ground and excited states of adjacent wells alternated with intrawell energy relaxation.
TL;DR: Absorption, gain, and luminescence spectra of quasi-two-dimensional electron-hole plasmas in semiconductor quantum-well structures are calculated as functions of the plasma density and temperature and implications for the theory of quantum- well lasers are discussed.
Abstract: Absorption, gain, and luminescence spectra of quasi-two-dimensional electron-hole plasmas in semiconductor quantum-well structures are calculated as functions of the plasma density and temperature. Self-energy corrections and the effects of multiple electron-hole scattering are evaluated for a statically screened Coulomb interaction. The Bethe-Salpeter equation for the electron-hole pair propagator is solved both numerically and analytically using a method developed by Noyes. The resulting spectra deviate considerably from the corresponding free-particle spectra, due to the strong pair fluctuations in two dimensions. Implications for the theory of quantum-well lasers are discussed.
TL;DR: In this paper, Si3N4 masking stripes and SiO2 defect (vacancy) sources were used to realize room-temperature continuous AlxGa1−xAs−GaAs quantum well heterostructure lasers.
Abstract: Impurity‐free selective layer disordering, utilizing Si3N4 masking stripes and SiO2 defect (vacancy) sources, is used to realize room‐temperature continuous AlxGa1−xAs‐GaAs quantum well heterostructure lasers.
TL;DR: In this paper, the binding energy of hydrogenic impurites in a quantum well wire has been calculated as a function of the width of the wire and the location of the impurity with respect to the axis of wire.
Abstract: The binding energy of hydrogenic impurites in a quantum well wire has been calculated as a function of the width of the quantum well wire and the location of the impurity with respect to the axis of the wire. The calculations have been preformed using a variational wave function which takes into account the confinement of the carriers in the wire. For the confining potential used in our calculations, we have used the models of either an infinite potential well or a finite potential well whose depth is detemined by the discontinuity of the band gas in the quantum well wire and the cladding. For the infinite potential well model, the binding energy continues to increase as the radius of the wire decreases while in the finite potential well model, the binding energy reaches a peak value as the wire radius decreases and then decreases to a value characteristic of the cladding. The binding energy also depends upon the location of the impurity in the wire and is a maximum when the impurity is located on the axi...
TL;DR: In this article, the authors reported optical dephasing of two-dimensional excitons in single quantum wells by means of time-resolved degenerate-four-wave mixing and transmission experiments in the temperature range below 80 K.
Abstract: We report optical dephasing of two-dimensional excitons in $\mathrm{GaAs}\ensuremath{-}{\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ single quantum wells by means of time-resolved degenerate-four-wave mixing and transmission experiments in the temperature range below 80 K. The observed absorption linewidths correspond directly to the excitonic phase coherence times, confirming the homogeneous broadening of the excitonic absorption. A linear temperature dependence of the homogeneous linewidth indicates acoustic-phonon scattering as the broadening mechanism.
TL;DR: In this article, the basic concepts and first-order growth model derived from the RHEED intensity oscillation technique are described and the limitations imposed by the experimentally demonstrated multiple-scattering nature of the diffraction process are indicated.
TL;DR: In this article, the photoluminescence (PL) linewidths at 2 K were the narrowest that have been ever reported for Ga0.47In0.53As quantum wells grown by any technique.
Abstract: We have prepared by chemical beam epitaxy extremely high quality Ga0.47In0.53As/InP quantum wells with thickness as thin as 6 A. Emission as short as 1.09 μm at 2 K (1.14 μm at 300 K) was obtained. Very sharp intense efficient luminescence peaks due to excitonic transitions were obtained from all quantum wells. The photoluminescence (PL) linewidths at 2 K were the narrowest that have been ever reported for Ga0.47In0.53As quantum wells grown by any technique. In fact, these Ga0.47In0.53As quantum well linewidths are at least equal to the narrowest linewidths ever reported for the perfected GaAs/AlAs and GaAs/AlxGa1−xAs quantum wells. These linewidths indicate the ‘‘effective’’ interface roughness to be 0.12 lattice constant, which can be interpreted as that the quantum well was largely consisting of a big domain of the same thickness Lz perforated with a small fraction of small domains of (Lz+a0/2), where a0 (=5.86 A) is the lattice constant. No broadening due to band filling from impurities was found. All...
TL;DR: In this paper, a detailed study of the optical properties of InGaAs-InP single quantum wells (QWS) grown by atmospheric-pressure metal-organic chemical vapour deposition is described.
Abstract: A detailed study of the optical properties of InGaAs-InP single quantum wells (QWS) grown by atmospheric-pressure metal-organic chemical vapour deposition is described. Photoluminescence (PL), photoluminescence excitation (PLE), photoconductivity (PC) and electroreflectance (ER) are employed to study both undoped and modulation-doped quantum wells. The role of extrinsic processes in determining the low-temperature PL spectra is demonstrated from the variation of peak position and linewidth with temperature. The best PL linewidth obtained for a 150 AA well is 5.3 meV, fairly close to the limit imposed by alloy fluctuations in the InGaAs. The role of free carriers in the undoped QWS in determining the energy threshold for optical absorption is demonstrated from a comparison of PLE and PC spectra. Lineshape fitting of the PL spectra is described, and it is deduced that at 160K recombination processes in both doped and undoped QWS proceed with wavevector conservation, although at lower temperatures highly anomalous lineshapes are found in modulation-doped samples. The observation of a threshold in PC spectra under forward bias is interpreted as a transition from the valence-band well to the top of the conduction well. The ratio of the conduction- to valence-band discontinuities is deduced to be approximately 0.4:0.6.
TL;DR: In this article, the authors investigated the currentvoltage characteristics of the double barrier, resonant tunneling structure, using a self-consistent method, and noted the significance of the effects of band bending and buildup of space charge in the quantum well.
Abstract: We investigated the current‐voltage characteristics of the double barrier, resonant tunneling structure, using a self‐consistent method. We note the significance of the effects of band bending and buildup of space charge in the quantum well. For the peak current, our calculated results agree with the measured results very well. However, the measured valley current is much greater than the calculated values.
TL;DR: In this paper, the existence of two-dimensional (2D) bulk-type double-interface-type and guided-type longitudinal optical (LO) modes in polar semiconductor heterostructures is investigated.
Abstract: A continuum theory is employed for investigating the longitudinal optical (LO) modes in polar semiconductor heterostructures. Particular emphasis is laid on the symmetric double heterostructure (DHS) such as occurs in a semiconductor quantum well. The existence of two-dimensional (2D) bulk-type double-interface-type and guided-type LO modes is examined for this case and their characteristic dispersion relations derived. It is shown with reference to a typical GaAs quantum well that the presence of at most two double-interface modes and a finite number of guided LO modes depends on the difference between the squares of the limiting bulk LO frequencies of the two materials. The implications of the results for light scattering experiments and for the properties of electrons confined in quantum wells are pointed out and discussed.
TL;DR: In this paper, the photoluminescence spectra of GaAs quantum wells of widths 26 to 150 A\r{} were studied as a function of hydrostatic pressure (0--70 kbar) at 80 and 150 K.
Abstract: Photoluminescence spectra of GaAs quantum wells of widths 26 to 150 A\r{} are studied as a function of hydrostatic pressure (0--70 kbar) at 80 and 150 K. The pressure coefficients of both the heavy- and light-hole excitons are found to decrease with decreasing well width. The direct to indirect conduction-band crossover, leading to the formation of type-II heterostructures, occurs at higher pressures for wider wells. A transition associated with the X conduction band in quantum-well structures is observed and its pressure dependence is established. Correlating this transition to barrier-to-well recombination determines the valence-band offset.
TL;DR: The first resonant tunneling bipolar transistor (RBT) was reported in this paper, which is a wide-gap emitter with two AlAs barriers between the emitter and the collector.
Abstract: The first resonant tunneling bipolar transistor (RBT) is reported. The AlGaAs/GaAs wide-gap emitter device, grown by molecular beam epitaxy (MBE), contains a GaAs quantum well and two AlAs barriers between the emitter and the collector. In the common emitter configuration, when the base current exceeds a threshold value, a large drop in the collector current (corresponding to a quenching of the current gain β) is observed at room temperature, along with a pronounced negative conductance as a function of the collector-emitter voltage. These striking characteristics are caused by the quenching of resonant tunneling through the double barrier as the conduction band edge in the emitter is raised above the bottom of the first quantized subband of the well. Single-frequency oscillations are observed at 300 K. The inherent negative transconductance of these new functional devices is extremely valuable for many logic and signal processing applications.
TL;DR: In this article, a series of MBE-grown single-quantum-well structures (SQWHs) consisting of an unintentionally doped, highly strained (e∼2%) In0.28Ga0.72As quantum well sandwiched between GaAs confining layers are examined using low-temperature photoluminescence techniques.
Abstract: Strain and quantum‐size effects in pseudomorphic InxGa1−xAs–GaAs single‐quantum‐well heterostructures (SQWHs) are examined using low‐temperature photoluminescence techniques. Strain effects in InxGa1−xAs epitaxial layers are first described, then photoluminescence data for a series of MBE‐grown pseudomorphic SQWHs are presented and discussed. Each SQWH consists of an unintentionally doped, highly strained (e∼2%) In0.28Ga0.72As quantum well sandwiched between GaAs confining layers. The structures were grown consecutively under identical conditions, with quantum‐well thicknesses ranging from 17 to 430 A. The thinner quantum‐well structures exhibit luminescence characteristics indicative of high‐quality material (photoluminescence half width ∼6 meV for Lz ∼17 A), whereas significant broadening and eventual quenching of the photoluminescence peak is observed as alloy layer thicknesses approach and exceed the critical value. Quantum‐well luminescence from the thinner (Lz ≤38 A) SQWHs is dominated by a single, ...
IBM1
TL;DR: A two-dimensional magnetotunneling effect which manifests itself as periodic structures in the current-voltage characteristics, with a period proportional to the electron cyclotron energy in the GaAs quantum well, from which the electron effective mass is determined.
Abstract: We report the observation of resonant tunneling of electrons through Landau levels in double-barrier GaAlAs-GaAs-GaAlAs heterostructures, in the presence of a strong magnetic field perpendicular to the interfaces. This is a two-dimensional magnetotunneling effect which manifests itself as periodic structures in the current-voltage characteristics, with a period proportional to the electron cyclotron energy in the GaAs quantum well, from which the electron effective mass is determined.
TL;DR: In this article, a new semiconductor structure that can be fabricated by present day technology and can lead to large quantum interference effects with potential device applications is proposed and analyzed, which can be used for quantum computing applications.
Abstract: In this letter we propose and analyze a new semiconductor structure that can be fabricated by present day technology and can lead to large quantum interference effects with potential device applications.
TL;DR: In this paper, the threshold current density of single quantum well (SQW) GaAs/GaAlAs was calculated, taking into account the carrier populations of the confining layer.
Abstract: The threshold current density of single quantum well (SQW) GaAs/GaAlAs lasers is calculated, taking into account the carrier populations of the confining layer. We find that these populations are significant when compared to those of the quantum well. This effect explains the better performance of the graded‐index separate confinement SQW laser when compared to the separate confinement heterostructure laser, as well as the T0 performance of such lasers.