Showing papers on "Quantum well published in 1999"
TL;DR: In this paper, the transition between the regimes of cw mode locking and Q-switched mode locking was investigated, and an extended theory that took into account nonlinear soliton-shaping effects and gain filtering was developed.
Abstract: The use of a saturable absorber as a passive mode locker in a solid-state laser can introduce a tendency for Q-switched mode-locked operation. We have investigated the transition between the regimes of cw mode locking and Q-switched mode locking. Experimental data from Nd:YLF lasers in the picosecond domain and soliton mode-locked Nd:glass lasers in the femtosecond domain, both passively mode locked with semiconductor saturable absorber mirrors, were compared with predictions from an analytical model. The observed stability limits for the picosecond lasers agree well with a previously described model, while for soliton mode-locked femtosecond lasers we have developed an extended theory that takes into account nonlinear soliton-shaping effects and gain filtering. © 1999 Optical Society of America [S0740-3224(99)01001-2] OCIS codes: 140.3580, 140.4050, 140.3540, 140.7090.
809 citations
TL;DR: In this paper, a self-assembling method was used to grow InAs quantum dots with size fluctuations of less than 4% on GaAs using the self-assembly method and the photoluminescence linewidth was reduced to 21 meV at room temperature.
Abstract: InAs quantum dots with size fluctuations of less than 4% were grown on GaAs using the self-assembling method. By covering the quantum dots with In0.2Ga0.8As or In0.2Al0.8As, strain in InAs dots can be partly reduced due to relaxation of lattice constraint in the growth direction. This results in low-energy emission (about 1.3 μm) from the quantum dots. The photoluminescence linewidth can be reduced to 21 meV at room temperature. This width is completely comparable to the theoretical limit of a band-to-band emission from a quantum well at room temperature. Because the dots can be uniformly covered by the strain reducing layers, factors that degrade size uniformity during coverage, such as compositional mixing or segregation, will be suppressed, allowing for an almost ideal buried quantum dot structure.
551 citations
TL;DR: In this paper, the authors review the nonlinear optical properties of semiconductor quantum wells that are grown inside high-Q Bragg-mirror microcavities and explain the Coulomb interacting electron-hole system in the quantum well.
Abstract: The authors review the nonlinear optical properties of semiconductor quantum wells that are grown inside high-Q Bragg-mirror microcavities. Light-matter coupling in this system is particularly pronounced, leading in the linear regime to a polaritonic mixing of the excitonic quantum well resonance and the single longitudinal cavity mode. The resulting normal-mode splitting of the optical resonance is observed in reflection, transmission, and luminescence experiments. In the nonlinear regime the strong light-matter coupling influences the excitation-dependent bleaching of the normal-mode resonances for nonresonant excitation, leads to transient saturation and normal-mode oscillations for resonant pulsed excitation and is responsible for the density-dependent signatures in the luminescence characteristics. These and many more experimental observations are summarized and explained in this review using a microscopic theory for the Coulomb interacting electron-hole system in the quantum well that is nonperturbatively coupled to the cavity light field.
492 citations
TL;DR: In this article, the authors discuss the background theory, role of spontaneous polarization in this context, and the practical implications of built-in polarization fields in nitride nanostructures.
Abstract: Huge built-in electric fields have been predicted to exist in wurtzite III-V nitrides thin films and multilayers. Such fields originate from heterointerface discontinuities of the macroscopic bulk polarization of the nitrides. Here we discuss the background theory, the role of spontaneous polarization in this context, and the practical implications of built-in polarization fields in nitride nanostructures. To support our arguments, we present detailed self-consistent tight-binding simulations of typical nitride quantum well structures in which polarization effects are dominant.
469 citations
TL;DR: In this paper, the lowest room-temperature threshold current density, 26 A/cm/sup 2 ), of any semiconductor diode laser was reported for a quantum dot device with a single InAs dot layer contained within a strained In/sub 0.85/As quantum well.
Abstract: The lowest room-temperature threshold current density, 26 A/cm/sup 2/, of any semiconductor diode lasers is reported for a quantum dot device with a single InAs dot layer contained within a strained In/sub 0.15/Ga/sub 0.85/As quantum well. The lasers are epitaxially grown on a GaAs substrate, and the emission wavelength is 1.25 /spl mu/m.
469 citations
TL;DR: In this article, a study of quantum box transitions coupled to three-dimensionalally confined photonic modes in pillar microcavities is presented, focusing on the conditions for achieving a vacuum-field Rabi splitting.
Abstract: A study of quantum box transitions coupled to three-dimensionally confined photonic modes in pillar microcavities is presented, focusing on the conditions for achieving a vacuum-field Rabi splitting. For a single InAs quantum box the oscillator strength is a factor of ten too small for being in strong coupling. A calculation of exciton states localized to monolayer fluctuations in quantum wells leads to much larger values of the oscillator strengths. Single localized excitons embedded in state-of-the-art micropillars can be in strong-coupling regime with a vacuum-field Rabi splitting.
397 citations
TL;DR: In this article, the lateral size of InAs islands has been found to be approximately 1.5 times larger as compared to the InAs/GaAs case, whereas the island heights and surface densities were close in both cases.
Abstract: InAs self-organized quantum dots inserted in InGaAs quantum well have been grown on GaAs substrates by molecular beam epitaxy. The lateral size of the InAs islands has been found to be approximately 1.5 times larger as compared to the InAs/GaAs case, whereas the island heights and surface densities were close in both cases. The quantum dot emission wavelength can be controllably changed from 1.1 to 1.3 μm by varying the composition of the InGaAs quantum well matrix. Photoluminescence at 1.33 μm from vertical optical microcavities containing the InAs/InGaAs quantum dot array was demonstrated.
359 citations
TL;DR: In this article, a 3-nm InGaN/GaN quantum well (QW) is positioned 12 nm from an 8-nm silver layer, well within the surface plasmon fringing field depth.
Abstract: The coincidence in excitation energy between surface plasmons on silver and the GaN band gap is exploited to couple the semiconductor spontaneous emission into the metal surface plasmons. A 3-nm InGaN/GaN quantum well (QW) is positioned 12 nm from an 8-nm silver layer, well within the surface plasmon fringing field depth. A spectrally sharp photoluminescence dip, by a factor \ensuremath{\approx}55, indicates that electron-hole energy is being rapidly transferred to plasmon excitation, due to the spatial overlap between the semiconductor QW and the surface plasmon electric field. Thus, spontaneous emission into surface plasmons is \ensuremath{\approx}55 times faster than normal spontaneous emission from InGaN quantum wells. If efficient antenna structures can be incorporated into the metal film, there could be a corresponding increase in external light emission efficiency.
316 citations
TL;DR: In this article, the ground state gain is determined from cavity mode Fabry-Perot modulation for InAs quantum-dot laser emitting at 1.22 /spl mu/m.
Abstract: Amplified spontaneous emission measurements are investigated below threshold in InAs quantum-dot lasers emitting at 1.22 /spl mu/m. The dot layer of the laser was grown in a strained quantum well (QW) on a GaAs substrate. Ground state gain is determined from cavity mode Fabry-Perot modulation. As the injection current increases, the gain rises super-linearly while changes in the index of refraction decrease. Below the onset of gain saturation, the linewidth enhancement factor is as small as 0.1, which is significantly lower than that reported for QW lasers.
305 citations
TL;DR: In this article, the potential of low dimensional thermoelectric materials for enhanced performance is reviewed, with particular attention given to quantum wells and quantum wires, and the high potential of bismuth as a low-dimensional material is discussed.
Abstract: The promise of low dimensional thermoelectric materials for enhanced performance is reviewed, with particular attention given to quantum wells and quantum wires. The high potential of bismuth as a low-dimensional thermoelectric material is discussed.
282 citations
TL;DR: In this article, a strain-balance multiquantum well (MQW) was used to enhance the GaAs solar cell efficiency using a p-i-n diode structure.
Abstract: A strain-balance multiquantum well (MQW) approach to enhance the GaAs solar cell efficiency is reported. Using a p-i-n diode structure, the strain-balanced GaAsP/InGaAs MQW is grown on a GaAs substrate and equals a good GaAs cell in terms of power conversion efficiency. The cell design is presented together with measurements of the forward bias dark current density, quantum efficiency, and 3000 K light-IV response. Cell efficiencies under standard air mass (AM) 1.5 and AM 0 illumination are projected from experimental data and the suitability of this cell for enhancing GaInP/GaAs tandem cell efficiencies is discussed.
TL;DR: In this paper, the free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum well lasers is investigated via a selfconsistent tight-binding approach.
Abstract: The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum well lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectricpolarization fields, thus inducing a “field-free” band profile. Our results explain some heretofore puzzling experimental data on nitride lasers, such as the unusually high lasing excitation thresholds and emission blue shifts for increasing excitation levels.
TL;DR: In this article, the role of the sample structure geometry on the electric field is exemplified by changing the thickness of the AlGaN barriers in multiple-QW structures and electrostatic arguments well account for the overall trends of the electric-field variations.
Abstract: AlGaN/GaN quantum well (QW) structures are grown on c-plane sapphire substrates by molecular beam epitaxy. Control at the monolayer scale of the well thickness is achieved and sharp QW interfaces are demonstrated by the low photoluminescence linewidth. The QW transition energy as a function of the well width evidences a quantum-confined Stark effect due to the presence of a strong built-in electric field. Its origin is discussed in terms of piezoelectricity and spontaneous polarization. Its magnitude versus the Al mole fraction is determined. The role of the sample structure geometry on the electric field is exemplified by changing the thickness of the AlGaN barriers in multiple-QW structures. Straightforward electrostatic arguments well account for the overall trends of the electric-field variations.
TL;DR: The mechanism for low-temperature photoluminescence (PL) emissions in GaNAs epilayers and GaAs/GaNxAs1−x quantum well (QW) structures grown by molecular-beam epitaxy is studied in detail, employing PL, PL excitation, and time-resolved PL spectroscopies as discussed by the authors.
Abstract: The mechanism for low-temperature photoluminescence (PL) emissions in GaNAs epilayers and GaAs/GaNxAs1−x quantum well (QW) structures grown by molecular-beam epitaxy is studied in detail, employing PL, PL excitation, and time-resolved PL spectroscopies. It is shown that even though quantum confinement causes a strong blueshift of the GaNAs PL emission, its major characteristic properties are identical in both QW structures and epilayers. Based on the analysis of the PL line shape, its dependence on the excitation power and measurement temperature, as well as transient data, the PL emission is concluded to be caused by a recombination of excitons trapped by potential fluctuations in GaNAs.
TL;DR: In this article, a quasi-two-dimensional optical system consisting of a triangular array of air cylinders etched through a laser-like Ga(Al)As waveguiding heterostructure is described.
Abstract: We describe experiments on a quasi-two dimensional (2-D) optical system consisting of a triangular array of air cylinders etched through a laser-like Ga(Al)As waveguiding heterostructure. Such a configuration is shown to yield results very well approximated by the infinite 2-D photonic crystal (PC). We first present a set of measurements of the optical properties (transmission, reflection, and diffraction) of slabs of these photonic crystals, including the case of in-plane Fabry-Perot cavities formed between two such crystals. The measurement method makes use of the guided photoluminescence of embedded quantum wells or InAs quantum dots to generate an internal probe beam. Out-of-plant, scattering losses are evaluated by various means. In a second part, in-plane micrometer-sized photonic boxes bounded by circular trenches or by two-dimensional photonic crystal are probed by exciting spontaneous emission inside them. The high quality factors observed in such photon boxes demonstrate the excellent photon confinement attainable in these systems and allow to access the detail of the modal structure. Last, some perspectives for applications are offered.
TL;DR: In this paper, self-assembled InAs-GaAs quantum dots are used in photoconductive intersubband detectors in the far-infrared for the measurement of far-in-infra-rared absorption.
Abstract: The use of self-assembled InAs-GaAs quantum dots in photoconductive intersubband detectors in the far-infrared is presented. Far-infrared absorption is observed in self-assembled quantum dots in the 6-18-/spl mu/m range for subband-subband and subband-continuum transitions. Photoconductive quantum-dot intersubband detectors were fabricated and demonstrate tunable operating wavelengths between 6-18 /spl mu/m using subband-subband or subband-continuum transitions. The use of AlAs barriers allows further tuning to shorter wavelengths of 3-7 /spl mu/m. Subband-continuum quantum dot intersubband detectors show encouraging normal incidence performance characteristics at T=40 K, with responsivities of 10-100 mA/W, detectivities of 1-10 /spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W and large photoconductive gain up to g=12 for a ten-layer quantum-dot heterostructure. With improvements in device structure, self-assembled quantum dots can be expected to provide intrinsic normal incidence broad-band detectors with advantages over quantum wells.
TL;DR: In this article, the present status of the rapidly developing field of semiconductor laser diodes based on self-organized quantum dots (QDs) is reviewed, and three applications of large commercial interest are discussed in detail: 1300nm QD laser on GaAs substrate, QD surface emitting lasers, and high power QD lasers.
Abstract: We review the present status of the rapidly developing field of semiconductor laser diodes based on self-organized quantum dots (QDs). Several milestones have been achieved since the first realization of such a device in 1994: above room-temperature cw operation, the lowest threshold current density of any semiconductor laser diode, high temperature stability, an extended wavelength range on GaAs substrate and high power operation. After a brief introduction we discuss the tremendous advances in epitaxial growth, device performance, and theoretical understanding of QD lasers. Three applications of large commercial interest are discussed in detail: 1300 nm QD lasers on GaAs substrate, QD surface emitting lasers, and high power QD lasers. Finally, we give an outlook on future developments.
TL;DR: In this article, a spectrum of optoelectronic properties of and uses for semi-insulating semiconductor heterostructures and thin films, including epilayers and quantum wells, are discussed.
Abstract: This review covers a spectrum of optoelectronic properties of and uses for semi-insulating semiconductor heterostructures and thin films, including epilayers and quantum wells. Compensation by doping, implantation, and nonstoichiometric growth are described in terms of the properties of point defects and Fermi level stabilization and pinning. The principal optical and optoelectronic properties of semi-insulating epilayers and heterostructures, such as excitonic electroabsorption of quantum-confined excitons, are described, in addition to optical absorption by metallic or semimetallic precipitates in these layers. Low-temperature grown quantum wells that have an arsenic-rich nonstoichiometry and a supersaturated concentration of grown-in vacancies are discussed. These heterostructures experience transient enhanced diffusion and superlattice disordering. The review discusses the performance of optoelectronic heterostructures and microcavities that contain semi-insulating layers, such as buried heterostructure stripe lasers, vertical cavity surface emitting lasers, and optical electroabsorption modulators. Short time-scale applications arise from the ultrashort carrier lifetimes in semi-insulating materials, such as in photoconductors for terahertz generation, and in saturable absorbers for mode-locking solid state lasers. This review also comprehensively describes the properties and applications of photorefractive heterostructures. The low dark-carrier concentrations of semi-insulating heterostructures make these materials highly sensitive as dynamic holographic thin films that are useful for adaptive optics applications. The high mobilities of free carriers in photorefractive heterostructures produce fast dielectric relaxation rates that allow light-induced space-charge gratings to adapt to rapidly varying optical fringe patterns, canceling out environmental noise during interferometric detection in laser-based ultrasound, and in optical coherence tomography. They are also the functional layers in high-sensitivity dynamic holographic materials that replace static holograms in Fourier imaging systems and in experimental Tbit/s optical systems. Semi-insulating heterostructures and their applications have attained a degree of maturity, but many critical materials science issues remain unexplored.
TL;DR: In this paper, the authors demonstrated room temperature lasing from optically pumped single defects in a two-dimensional (2D) photonic bandgap (PBG) crystal is demonstrated, where high-Q optical microcavities are formed by etching a triangular array of air holes into a half-wavelength multiquantum-well waveguide.
Abstract: Room temperature lasing from optically pumped single defects in a two-dimensional (2-D) photonic bandgap (PBG) crystal is demonstrated. The high-Q optical microcavities are formed by etching a triangular array of air holes into a half-wavelength thick multiquantum-well waveguide. Defects in the 2-D photonic crystal are used to support highly localized optical modes with volumes ranging from 2 to 3 (/spl lambda//2n)/sup 3/. Lithographic tuning of the air hole radius and the lattice spacing are used to match the cavity wavelength to the quantum-well gain peak, as well as to increase the cavity Q. The defect lasers were pumped with 10-30 ns pulses of 0.4-1% duty cycle. The threshold pump power was 1.5 mW (/spl ap/500 /spl mu/W absorbed).
TL;DR: In this paper, the authors demonstrate that even in unstrained GaN quantum wells with AlGaN barriers, there exist giant electric fields as high as 1.5 MV/cm.
Abstract: We demonstrate that, even in unstrained GaN quantum wells with AlGaN barriers, there exist giant electric fields as high as 1.5 MV/cm. These fields, resulting from the interplay of the piezoelectric and spontaneous polarizations in the well and barrier layers due to Fermi level alignment, induce large redshifts of the photoluminescence energy position and dramatically increase the carrier lifetime as the quantum well thickness increases.
TL;DR: In this article, a spintronic semiconductor field effect transistor was presented, which was made from magnetic permalloy thin films with different coercive fields so that they could be magnetized either parallel or antiparallel to each other in different applied magnetic fields.
Abstract: We present a spintronic semiconductor field-effect transistor. The injector and collector contacts of this device were made from magnetic permalloy thin films with different coercive fields so that they could be magnetized either parallel or antiparallel to each other in different applied magnetic fields. The conducting medium was a two-dimensional electron gas (2DEG) formed in an AlSb/InAs quantum well. Data from this device suggest that its resistance is controlled by two different types of spin-valve effect: the first occurring at the ferromagnet-2DEG interfaces; and the second occurring in direct propagation between contacts.
TL;DR: In this paper, a low-threshold current density of 520 A/cm2 was achieved for an InGaAsN:Sb/GaAs single quantum well 1.2 μm laser diode at room temperature under pulsed operation.
Abstract: InGaAsN:Sb/GaAs quantum wells (QWs) were grown by solid-source molecular beam epitaxy using a N2 radio-frequency plasma source. Photoluminescence reveals an enhancement in the optical properties of InGaAsN/GaAs QWs by the introduction of Sb flux during growth. X-ray diffraction and reflection high-energy electron diffraction analyses indicate that Sb acts as a surfactant. This technique was used to improve the performance of long-wavelength InGaAsN laser diodes. A low-threshold current density of 520 A/cm2 was achieved for an InGaAsN:Sb/GaAs single quantum well 1.2 μm laser diode at room temperature under pulsed operation.
TL;DR: In this article, a low-temperature photoluminescence study showed that the behavior of transition energy versus the barrier width is the opposite of that currently obtained for more usual III-V semiconductor compounds like arsenides: when decreasing the barrier thickness, a blueshift is observed.
Abstract: Electrostatic effects which take place in group-III nitrides in their wurtzite crystallographic phase have important consequences on the optical properties of (Al,Ga)N/GaN multiple quantum wells A low-temperature photoluminescence study shows that the behavior of the transition energy versus the barrier width is the opposite of that currently obtained for more usual III-V semiconductor compounds like arsenides: when decreasing the barrier thickness, a blueshift is observed This behavior is attributed to a redistribution across the samples of the huge built-in electric field (several hundreds kV/cm) induced by the polarization difference between wells and barriers The trend of the barrier-width dependence of the electric field is reproduced by using simple electrostatic arguments However, the field magnitude is higher than that predicted taking account only piezoelectric effects This result points out the role of the spontaneous polarization in wurtzite nitrides
Book•
21 Jul 1999
TL;DR: Free-Carrier Theory, Coulomb effects, Correlation effects, Bulk Band Structures, Quantum Wells, and Quantum Wells have been studied in the literature as mentioned in this paper for a wide range of applications.
Abstract: 1 Basic Concepts- 2 Free-Carrier Theory- 3 Coulomb Effects- 4 Correlation Effects- 5 Bulk Band Structures- 6 Quantum Wells- 7 Applications- References
TL;DR: In this article, the authors applied optimized low-temperature metal organic vapour phase epitaxy (MOVPE) using the group V sources 1,1-dimethylhydrazine (UDMHy) in combination with tertiarybutylarsine (TBAs) to achieve record low threshold current densities of 0.18 and 0.16 W/A per facet, respectively, for 800 µm long broad area lasers emitting at 1.28 and 1.38 µm, respectively.
Abstract: (GaIn)(NAs)/GaAs single quantum well (SQW) broad area lasers with emission wavelengths at 1.28 and 1.38 µm at room temperature on GaAs substrates have been realised by applying optimised low-temperature metal organic vapour phase epitaxy (MOVPE) using the group V sources 1,1-dimethylhydrazine (UDMHy) in combination with tertiarybutylarsine (TBAs). Record-low threshold current densities of 0.8 and 2.2 kA/cm2, together with high differential efficiencies of 0.18 and 0.16 W/A per facet, are obtained for 800 µm long broad area lasers emitting at 1.28 and 1.38 µm, respectively.
TL;DR: In this paper, the emission mechanisms of strained InGaN quantum wells (QWs) were shown to vary depending on the well thickness L and InN molar fraction x, where Si-doping was found to improve the interface quality and surface morphology, resulting in an efficient carrier transfer from high to low bandgap energy portions of the well.
Abstract: The emission mechanisms of strained InGaN quantum wells (QWs) were shown to vary depending on the well thickness L and InN molar fraction x . The QW resonance energy was shifted to lower energy by the quantum confined Stark effect (QCSE) due to the internal piezoelectric field, F PZ . The absorption spectrum was modulated by QCSE and quantum-confined Franz–Keldysh effect (QCFK) for the wells, in which, for the first approximation, the product of F PZ and L (potential drop across the well) exceeds the valence band discontinuity, Δ E V . In this case, dressed holes are confined in the triangular potential well formed at one side of the well. This produces apparent Stokes-like shift (vertical component). The QCFK further modulated the absorption energy for the wells with L greater than the three dimensional free exciton Bohr radius, a B . For the wells having high InN content ( F PZ × L >Δ E V , Δ E C ), electron and hole confined levels drop into the triangular potential wells formed at opposite sides of the wells, which reduces the wavefunction overlap. Doping of Si in the barriers partially screens F PZ resulting in a smaller Stokes-like shift, shorter recombination decay time, and higher emission efficiency. Si-doping was found to improve the interface quality and surface morphology, resulting in an efficient carrier transfer from high to low bandgap energy portions of the well. Effective in-plane localization of carriers in quantum disk size potential minima, which are produced by nonrandom alloy potential fluctuations enhanced by the large bowing parameter and F PZ , produces confined e–h pair whose wavefunctions are still overlapped. Their excitonic features are pronounced provided that L a B and F PZ × L E V (quantized exciton). Several cw laser wafers exhibit stimulated emission from these energy tail states even at room temperature.
TL;DR: In this article, the authors compared the optical properties of bulk GaN and InGaN quantum wells by comparing their optical properties as a function of threading dislocation (TD) density, which was controlled by lateral epitaxial overgrowth.
Abstract: The emission mechanisms of bulk GaN and InGaN quantum wells (QWs) were studied by comparing their optical properties as a function of threading dislocation (TD) density, which was controlled by lateral epitaxial overgrowth Slightly improved excitonic photoluminescence (PL) intensity was recognized by reducing TD density from 1010 cm−2 to less than 106 cm−2 However, the major PL decay time was independent of the TD density, but was rather sensitive to the interface quality or material purity These results suggest that TDs simply reduce the net volume of light-emitting area This effect is less pronounced in InGaN QWs where carriers are effectively localized at certain quantum disk size potential minima to form quantized excitons before being trapped in nonradiative pathways, resulting in a slow decay time The absence of any change in the optical properties due to reduction of TD density suggested that the effective band gap fluctuation in InGaN QWs is not related to TDs
TL;DR: In this article, optical properties of CdTe self-assembled quantum dots (SADs) grown by molecular beam epitaxy on ZnTe were investigated and the activation energy of the thermal quenching of SADs-related photoluminescence (PL) emission was found to be equal to 47 meV.
Abstract: We report on optical properties of CdTe self-assembled quantum dots (SADs) grown by molecular beam epitaxy on ZnTe. Formation of SADs was achieved by deposition of 1.5–2.5 monolayers of CdTe at a substrate temperature of 420 °C and by applying growth interrupts for few seconds in Cd flux. The resulting dots have a typical diameter of 2 nm and a sheet density of 1012 cm−2. At T=2 K the photoluminescence (PL) spectra consist of two emission lines. The high-energy line originates from excitonic recombination in a wetting layer while the low-energy emission PL band is assigned to recombination in SADs. The increase in temperature up to 70 K does not affect the SADs-related emission intensity. It shifts, however, the PL peak energy towards low energies and causes a significant narrowing of the PL linewidth, from 80 meV at 1.9 K to 50 meV at 130 K. The activation energy of the thermal quenching of SADs-related PL emission was found to be equal to 47 meV. This value is three times greater than the one observed in CdTe/ZnTe quantum wells, that is, 12–17 meV.
Patent•
16 Sep 1999TL;DR: In this article, a vertical geometry light emitting diode is described that is capable of emitting light in the red, green, blue, violet and ultraviolet portions of the electromagnetic spectrum.
Abstract: A vertical geometry light emitting diode is disclosed that is capable of emitting light in the red, green, blue, violet and ultraviolet portions of the electromagnetic spectrum. The light emitting diode includes a conductive silicon carbide substrate, an InGaN quantum well, a conductive buffer layer between the substrate and the quantum well, a respective undoped gallium nitride layer on each surface of the quantum well, and ohmic contacts in a vertical geometry orientation.