Showing papers on "Quantum well published in 1982"
TL;DR: In this paper, a new type of semiconductor laser is studied, in which injected carriers in the active region are quantum mechanically confined in two or three dimensions (2D or 3D), and the effects of such confinements on the lasing characteristics are analyzed.
Abstract: A new type of semiconductor laser is studied, in which injected carriers in the active region are quantum mechanically confined in two or three dimensions (2D or 3D). Effects of such confinements on the lasing characteristics are analyzed. Most important, the threshold current of such laser is predicted to be far less temperature sensitive than that of conventional lasers, reflecting the reduced dimensionality of electronic state. In the case of 3D‐QW laser, the temperature dependence is virtually eliminated. An experiment on 2D quantum well lasers is performed by placing a conventional laser in a strong magnetic field (30 T) and has demonstrated the predicted increase of T0 value from 144 to 313 °C.
3,069 citations
IBM1
TL;DR: In this paper, the ground exciton state in quantum wells has been investigated and the results obtained from a trial wave function not separable in spatial coordinates are shown to be valid throughout the entire well-thickness range, corresponding in the thin and thick limits to two and three-dimensional situations, respectively.
Abstract: Variational calculations are presented of the ground exciton state in quantum wells. For the GaAs-GaAlAs system, the results obtained from a trial wave function not separable in spatial coordinates are shown to be valid throughout the entire well-thickness range, corresponding in the thin and thick limits to two- and three-dimensional situations, respectively. For the InAs-GaSb system, in which electrons and holes are present in spatially separated regions, the exciton binding is substantially reduced. In the limit of thin wells, the binding energy is only about one-fourth of the two-dimensional value.
574 citations
TL;DR: In this paper, a momentum-conservation approximation was obtained for the scattering rates and momentum-relaxation rates of an electron in a quasi-two-dimensional quantum well interacting with acoustic, optical and intervalley modes via deformation potential and with longitudinal optical modes via the polar interaction.
Abstract: Approximate analytic expressions are obtained for the scattering rates and momentum-relaxation rates of an electron in a quasi-two-dimensional quantum well interacting with acoustic, optical and intervalley modes via the deformation potential and with longitudinal optical modes via the polar interaction. These analytic expressions are obtained using a momentum-conservation approximation. The threshold for optical phonon emission, unlike the case in the bulk, is abrupt. All scattering rates are energy-independent and are inversely proportional to L, the thickness of the well. The momentum-relaxation rate associated with the absorption of polar optical phonons, on the other hand, proves to be proportional to L. These properties are shown to lead to a negative differential resistance for pure polar mode scattering, and to the existence of a runaway field for deformation-potential scattering. The self-energy associated with the emission of polar optical phonons at absolute zero is shown to be divergent unless the polar interaction is screened, and some consequences of this for laser and other optical processes are pointed out. The description of scattering by perturbation theory breaks down in very narrow wells.
387 citations
TL;DR: In this article, a defect-free GaAs quantum well wires (QWW) with submicron dimensions using molecular beam epitaxy of GaAs and Ga1−xAlxAs were fabricated.
Abstract: As a first step toward the realization of a one‐dimensional carrier confining structure in semiconductors, we have fabricated GaAs quantum well wires (QWW) with submicron dimensions using molecular beam epitaxy of GaAs and Ga1−xAlxAs. The structural quality and dimensions of the QWW have been assessed by transmission electron microscopy showing that single crystal, defect‐free QWW, with dimensions as small as 200×200 A in cross section can be achieved. The optical properties measured by low‐temperature (T≳20°K) cathodoluminescence (CL) indicate a CL efficiency nearly as good as that of the quantum well material from which the QWW originated. A localization of the luminescence along the QWW axis is characteristic of QWW with sizes below a critical dimension (1.5 μm×200 A cross section). This luminescence localization and a shift of the intrinsic luminescence to lower energy in QWW structures are tentatively assigned to strain effects in these structures.
376 citations
TL;DR: In this article, low-temperature photoluminescence (PL) measurements have been performed in narrow GaAs-${\mathrm{Ga}}_{1\ensuremath{-}x{Al}}_{x}\mathrm {As}$ quantum wells subject to an electric field perpendicular to the well plane, showing two peaks associated with exciton and free-electron-to-impurity recombination.
Abstract: Low-temperature photoluminescence (PL) measurements have been performed in narrow GaAs-${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}\mathrm{As}$ quantum wells subject to an electric field perpendicular to the well plane. At low fields the PL spectra show two peaks associated, respectively, with exciton and free-electron-to-impurity recombination. With increasing field the PL intensity decreases, with the excitonic structure decreasing at a much faster rate, and becomes completely quenched at a field of a few tens of kV/cm. This is accompanied by a shift in the peak position to lower energies. The results are interpreted as caused by the field-induced separation of carriers and modification of the quantum energies. Variational calculations performed for isolated, finite quantum wells explain qualitatively the experimental observations.
246 citations
TL;DR: In this article, the binding energy of the free excitons in GaAs is increased by using a superlattice etalon, and the switching times are 20-40 ns.
Abstract: The quantum wells provided by a superlattice increase the binding energy of the free excitons in GaAs, permitting 300 K bistable operation of a superlattice etalon. The superlattice consists of 61 periods of 336 A GaAs and 401 A Ga0.73Al0.27As. The intensities required are about 1 mW/ ( μm)2 and the switching times are 20–40 ns, similar to the low‐temperature pure GaAs values. Room‐temperature operation of semiconductor etalons enhances the likelihood of all‐optical logic and switching.
213 citations
TL;DR: In this article, the exciton edge of the photoluminescence from a number of high-quality multiple-GaAs-quantum-well samples grown by molecular-beam epitaxy was examined.
Abstract: Careful examination of the exciton edge of the photoluminescence from a number of high-quality multiple-GaAs-quantum-well samples grown by molecular-beam epitaxy reveals at low temperatures a double peak whose splitting of approximately 1 meV decreases somewhat with increasing GaAs well width $L$. The higher-energy peak is due to the $n=1$ free-heavy-hole-exciton transition while the excitation intensity, temperature, and polarization dependences of the lower-energy peak suggest that it is due to biexcitons with a binding energy $B$ of about 1 meV. In support of the biexciton interpretation a theoretical calculation of $B(L)$ is presented. This calculation gives two-dimensional biexciton binding energies more than an order of magnitude larger than the three-dimensional calculated values.
148 citations
TL;DR: In this paper, the operation of a coupled multiple stripe quantum well injection laser array is described, which can produce up to 400 mW of continuous output power and 2.1 W of peak pulsed (75 ns) output power from an uncoated mirror facet.
Abstract: Operation of a coupled multiple stripe quantum well injection laser array is described. The device emits up to 400 mW of continuous output power and 2.1 W of peak pulsed (75 ns) output power from an uncoated mirror facet. Its far‐field pattern is invariant to over three times threshold, and over 140 mW cw are coupled into a 100‐μm core 0.3‐numerical aperture (N.A.) optical fiber.
99 citations
TL;DR: In this article, a model calculation of the threshold current of a laser in a quantum well structure is presented, where the band-to-band radiative recombination rate is calculated using a constant density of states and the k-selection rule.
Abstract: A model calculation of the threshold current of a laser in a quantum well structure is presented. The band‐to‐band radiative recombination rate is calculated using a constant density of states and the k‐selection rule. This calculation shows that the threshold current of a GaAs single quantum well laser has low‐temperature sensitivity (T0∼330 K for T>300 K). The calculated threshold current of a 200‐A‐wide GaAs single quantum well laser is ∼550 A/cm2. The results of the calculation are compared with experimental results.
95 citations
TL;DR: In this article, the first well of a GaAs quantum well was found to exhibit a "rough" (6 A≲δL≲15 A) first interface and an acceptor-like luminescing impurity in the first tens of angstroms of GaAs grown.
Abstract: Photoluminescence studies of GaAs‐AlxGa1−xAs heterostructures grown by molecular beam epitaxy (MBE) which contain one and two GaAs quantum wells suggest that in some of the samples the first well grown usually exhibits a ’’rough’’ (6 A≲δL≲15 A) first interface and an acceptorlike luminescing impurity in the first few tens of angstroms of GaAs grown. The luminescence may arise from carbon which accumulates on the AlxGa1−xAs ‐vacuum interface during growth and is then deposited in the first few unit cells of GaAs. The phenomenon discussed may be relevant to the problem of growing high electron mobility field‐effect transistor heterostructures by MBE with GaAs on the top.
92 citations
TL;DR: In this paper, the collective modes of the GaAs-GaAlAs superlattice with doped (or modulated doped) quantum wells were investigated and the wavevector-frequency dependent dielectric constant was investigated.
TL;DR: In this paper, the dynamics of carrier collection in quantum-well heterostructures were studied by photoemission experiments and Monte Carlo simulations, and it was shown that carrier scattering decreases rapidly for well sizes Lz ≲100 A. The energy distribution function of the carriers after collection exhibits significant structure with respect to multiples of the phonon energy.
Abstract: The dynamics of carrier collection in quantum‐well heterostructures are studied by photoemission experiments and Monte Carlo simulations. It is shown that carrier scattering decreases rapidly for well sizes Lz ≲100 A. The collection mechanism depends sensitively on details of the band structure. The energy distribution function of the carriers after collection exhibits significant structure with respect to multiples of the phonon energy. This feature is also reflected by the experimental results.
TL;DR: In this paper, a remarkable agreement was found between the experimental n=1 electron to heavy hole transition energies and those calculated with the simple rectangular well model, indicating that the Al-content changes at the interfaces over less than one unit cell.
Abstract: Ga1-xAlxAs?GaAs quantum wells are grown by MOVPE. Wells as narrow as 25 ? are made. Interface quality in relation to alloy clustering and abruptness in change of Al-content are characterized with the aid of luminescence spectrum measurements. A remarkable agreement is found between the experimental n=1 electron to heavy hole transition energies and those which are calculated with the simple rectangular well model. The results indicate that the Al-content changes at the interfaces over less than one unit cell.
Patent•
16 Jul 1982TL;DR: A superlattice semiconductor device consisting of a plurality of multi-dimensional charge carrier confinement regions of semiconductor material exhibiting relatively high charge carrier mobility and a low band gap is proposed in this article.
Abstract: A superlattice semiconductor device consisting of a plurality of multi-dimensional charge carrier confinement regions of semiconductor material exhibiting relatively high charge carrier mobility and a low band gap which are laterally located in a single planar layer of semiconductor material exhibiting a relatively low charge carrier mobility and high band gap and wherein the confinement regions have sizes and mutual separation substantially equal to or less than the appropriate deBroglie wavelength. The device, in its preferred form, comprises a thin film of semiconductor material selected from group II-VI or III-V compounds or silicon wherein there is formed laterally located cylindrically shaped periodic regions which are adapted to act as quantum well confinement regions for electrons.
TL;DR: In this article, a GaAs−GaAlAs single quantum well laser was fabricated, utilizing the graded-index separate confinement heterostructure to confine carriers and optical field, and very low threshold current densities were observed down to a well size of 75 A.
Abstract: Graded‐barrier GaAs‐GaAlAs single quantum well lasers have been fabricated, utilizing the graded‐index separate confinement heterostructure to confine carriers and optical field. Very low threshold current densities have been observed down to a well size of 75 A. The lowest threshold current density observed is 240 A/cm2 for a 100‐A heavily doped quantum well laser. This experimental value agrees very well with the calculated threshold current density obtained from detailed band calculation and is attributed to the enhanced gain‐current characteristic in these quantum well structures.
TL;DR: In this paper, the interband nonradiative Auger recombination in quantum-well InGaAsP/InP heterostructure lasers has been calculated and it is found that the Auger rate is much reduced in the quasi two-dimensional quantum well lasers.
Abstract: Interband nonradiative Auger recombination in quantum-well InGaAsP/InP heterostructure lasers has been calculated. It is found that the Auger rate is much reduced in the quasi two-dimensional quantum-well lasers. This suggests that the temperature sensitivity of quantum-well InGaAsP lasers is much less than ordinary structures with much higher values of T 0 at around room temperatures.
TL;DR: In this paper, photoluminescence attributed to excitons bound to neutral impurities has been observed from GaAs quantum wells in Al x Ga 1−x As-GaAs heterostructures grown by molecular beam epitaxy.
TL;DR: In this article, the authors reported low-threshold MO-CVD GaAlAs DH (∼7730 A) with symmetric stepped index cladding layers on both sides of a thin single quantum well active region.
Abstract: The letter reports low-threshold MO-CVD GaAlAs DH (∼7730 A) lasers containing Mg as the p-type dopant. The structure consists of symmetric stepped index cladding layers on both sides of a thin single quantum well (∼60 A) active region. Broad-area threshold current densities of 460 A cm−2 and 270 A cm−2 are achieved for cavity lengths of 250 and 500 μm, respectively. Broad-area room-temperature lasers without facet coatings emit in excess of 400 mW/facet CW output power.
TL;DR: In this article, a variational calculation of the hydrogenic impurity ground state in a quantum well is proposed, where the binding energy is calculated as a function of the well thickness and of the impurity position.
TL;DR: In this article, the parameters of a single quantum well laser have been further optimized, and for a quantum well thickness of 60 A, with outer confinement layers composed of Ga0.4Al0.6As, significantly lower threshold current densities have been achieved.
Abstract: In a recent publication we gave preliminary results on the lasing characteristics of a GRIN-SCH GaAs/GaAlAs laser grown by OM-VPE. The parameters of this single quantum well laser have now been further optimised, and for a quantum well thickness of 60 A, with outer confinement layers composed of Ga0.4Al0.6As, significantly lower threshold current densities have been achieved. For a broad-area laser of cavity length 413 μm (width 140 μm) the average threshold current density is 232 A cm−2, and this decreases to 121 A cm−2 for a chip length of 1788 μm. We believe that these are the lowest lasing threshold current densities that have yet been reported.
TL;DR: In this paper, the authors investigated the threshold current density and emission wavelength for broad area single quantum well double heterostructure (SQW DH) Ga1−xAlxAs lasers grown by MOCVD under pulsed operation at room temperature.
Abstract: Laser threshold current density and emission wavelength were investigated for broad area single quantum well double heterostructure (SQW DH) Ga1−xAlxAs lasers grown by metalorganic chemical vapor deposition (MOCVD) under pulsed operation at room temperature. The shortest lasing emission wavelength was 7065 A. At that wavelength, the threshold current density was 1 kA/cm2 for a Fabry–Perot diode of 500‐μm cavity length and the external differential quantum efficiency was 48%. These values are significantly better than those previously reported for Ga1−xAlxAs DH lasers operating under similar conditions at the same wavelengths. We attribute the improved performance in part to the quantum size effect (active layer thickness 400– 600 A).
TL;DR: In this paper, the radiative recombination rate in a quantum well structure was calculated using a constant density of states and the k-selection rule, and it was shown that the threshold current of a GaAs quantum well laser has low temperature sensitivity (T 0 330 K for T > 300 K).
Abstract: The radiative recombination rate in a quantum well structure is calculated using a constant density of states and the k-selection rule. This calculation shows that the threshold current of a GaAs quantum well laser has low temperature sensitivity (T0 330 K for T > 300 K).
TL;DR: Besides high pressure or bulk crystal composition change, a size-determined direct-indirect transition can be obtained in an AlxGa1−xAs (0⩽x ⩽0.1) quantum-well heterostructure (QWH), in fact, at higher energy (E∼2.05 eV) than in bulk AlxGe1−XAs (∼1.98 eV), which is demonstrated at 6700-6500 A on a QWH grown by metalorganic chemical vapor deposition (MOCVD) as discussed by the authors
Abstract: Besides high pressure or bulk crystal composition change, a size‐determined direct‐indirect transition can be obtained in an AlxGa1−xAs (0⩽x⩽0.1) quantum‐well heterostructure (QWH), in fact, at higher energy (E∼2.05 eV) than in bulk AlxGa1−xAs (∼1.98 eV). Laser operation is demonstrated at 6700–6500 A on a QWH grown by metalorganic chemical vapor deposition (MOCVD).
TL;DR: Theoretically estimated limiting electron densities for plasma-recombination lasers are shown to agree with experimentally measured values over a wavelength variation of nearly one decade as discussed by the authors, and it is shown that radiation trapping is not sufficient to restrict the electron density in recombination lasers that operate at wavelengths longer than about 100 nm.
Abstract: Theoretically estimated limiting electron densities for plasma‐recombination lasers are shown to agree with experimentally measured values over a wavelength variation of nearly one decade. Radiation trapping is found not to restrict the electron densities in recombination lasers that operate at wavelengths longer than about 100 nm. For wavelengths shorter than 150 nm predicted specific output energies for plasma‐recombination lasers may exceed those of excimer lasers.
TL;DR: In this paper, an experimental set-up for the observation of transient spectra and mode partition noise of InGaAsP injection lasers in real time is described, and the build-up times for the dominant mode in various lasers are compared.
Abstract: An experimental set-up for the observation of transient spectra and mode partition noise of InGaAsP injection lasers in real time is described. The build-up times for the dominant mode in various lasers are compared.
TL;DR: In this paper, the threshold current in 20 μm stripe GaxIn1−xAsyP1−y lasers operating at 1.3 μm wavelength decreases with increasing pressure, whereas the opposite effect occurs in lasers made of Ga 1−xAlxAs.
Abstract: The threshold current in 20 μm stripe GaxIn1−xAsyP1−y lasers operating at 1.3 μm wavelength decreases with increasing pressure, whereas the opposite effect occurs in lasers made of Ga1−xAlxAs The magnitude of the change observed in quaternary lasers is consistent with the presence of intervalence band absorption or Auger recombination, but not with the other mechanisms considered.
TL;DR: In this article, the integrated InGaAsP etched-mirror lasers are fabricated using liquid-phase epitaxy and a new material-selective chemical etching technique and the integrated devices have been operated as optically coupled lasers, photodiodes, and resonant optical amplifiers.
Abstract: Monolithically integrated InGaAsP heterostructure lasers ( \lambda = 1.3 \mu m) coupled to low-loss InGaAsP waveguides are described. The integrated InGaAsP etched-mirror lasers are fabricated using liquid-phase epitaxy and a new material-selective chemical etching technique. The integrated devices have been operated as optically coupled lasers, photodiodes, and resonant optical amplifiers. For lasers with two etched mirrors, differential transfer efficiencies as high as 8 percent have been measured for waveguide-coupled laser-photodiode pairs. The waveguide-coupled InGaAsP lasers with 12.5 \times 300 \mu m contact stripes and two etched mirrors have room-temperature threshold currents as low as 580 mA pulsed. Similarly fabricated etched-mirror lasers without the waveguide layer have threshold currents as low as 280 mA pulsed (25 μm stripewidth). In order to obtain lower threshold currents and stable transverse-mode characteristics, InGaAsP buried-heterostructure (BH) lasers with chemically etched mirrors have been fabricated. The etched-mirror BH lasers have threshold currents as low as 160 mA pulsed. Evaluation of the etched-mirror reflectivity for the material-selective-etched lasers yielded an estimated reflectivity R = 0.01-0.03 and scattering loss S = 0.6-0.8 . Similar evaluation of a BH laser with non-material-selective-etched mirrors gave an estimated reflectivity R = 0.11 and scattering loss S = 0.4 . Analysis of the mode reflectivity of nonideal double-heterostructure laser mirrors shows that the reflectivity is limited by misalignment (tilt) of the etched mirrors.
TL;DR: In this article, absorption and emission data on AlAs•GaAs and AlxGa1−xAs−GaAs quantum well heterostructure (QWH) laser diodes subjected to hydrostatic pressure (0-10 kbar) at 300 K were presented.
Abstract: Absorption data on AlAs‐GaAs and AlxGa1−xAs‐GaAs superlattices (SL’s) and emission data on AlxGa1−xAs‐GaAs quantum well heterostructure (QWH) laser diodes subjected to hydrostatic pressure (0–10 kbar) at 300 K are presented. Superlattice absorption data show that the confined‐particle transitions, which partition and ’’label’’ the Γ energy band high above the band edge, all move with the same pressure coefficient of 11.5 meV/kbar. (For bulk GaAs, the pressure coefficient is 12.5 meV/kbar.) The effect of the L indirect minima on the highest observed confined‐particle transitions is small; the effect of the X minima is large. At lower pressures, QWH diodes exhibit a pressure dependence similar to that of the free (unconstrained) SL’s. The data on QWH diodes demonstrate, however, a size‐dependent [Lz(GaAs)<500 A] shift in slope to a lower (8.5 meV/kbar) energy gap versus pressure coefficient at higher pressures. This change in slope can be explained by considering the effect on the light‐ and heavy‐hole subb...