Showing papers on "Quantum well published in 2005"
TL;DR: It is shown that under suitable growth conditions hexagonal V-shaped pits decorating the defects exhibit narrow sidewall quantum wells with an effective band gap significantly larger than that of the regular c-plane quantum wells.
Abstract: Despite the high density of threading dislocations generally found in (AlGaIn)N heterostructures, the light emission efficiency of such structures is exceptionally high. It has become common to attribute the high efficiency to compositional fluctuations or even phase separation in the active GaInN quantum well region. The resulting localization of charge carriers is thought to keep them from recombining nonradiatively at the defects. Here, we show that random disorder is not the key but that under suitable growth conditions hexagonal V-shaped pits decorating the defects exhibit narrow sidewall quantum wells with an effective band gap significantly larger than that of the regular c-plane quantum wells. Thereby nature provides a unique, hitherto unrecognized mechanism generating a potential landscape which effectively screens the defects themselves by providing an energy barrier around every defect.
396 citations
TL;DR: In this paper, a 32-fold increase in spontaneous emission rate of InGaN/GaN quantum well at 440 nm was observed by employing surface plasmons (SPs) probed by time-resolved photoluminescence spectroscopy.
Abstract: We observed a 32-fold increase in the spontaneous emission rate of InGaN/GaN quantum well (QW) at 440 nm by employing surface plasmons (SPs) probed by time-resolved photoluminescence spectroscopy. We explore this remarkable enhancement of the emission rates and intensities resulting from the efficient energy transfer from electron-hole pair recombination in the QW to electron vibrations of SPs at the metal-coated surface of the semiconductor heterostructure. This QW-SP coupling is expected to lead to a new class of super bright and high-speed light-emitting diodes (LEDs) that offer realistic alternatives to conventional fluorescent tubes.
346 citations
TL;DR: Tunneling induced quantum interference experienced by an incident probe in asymmetric double quantum wells can easily be modulated by means of an external control light beam and can be exploited to devise a novel all-optical ultrafast switch.
Abstract: Tunneling induced quantum interference experienced by an incident probe in asymmetric double quantum wells can easily be modulated by means of an external control light beam This phenomenon, which is here examined within the dressed-state picture, can be exploited to devise a novel all-optical ultrafast switch For a suitably designed semiconductor heterostructure, the switch is found to exhibit frequency bandwidths of the order of 01 THz and response and recovery times of about 1 ps
221 citations
TL;DR: In this paper, the Huang-Rhys factor extracted from the Fabry-Perot interference-free photoluminescence spectra has been compared with the results of a model calculation, yielding a value of approximately 2nm for the in-plane localization length scale of carriers.
Abstract: We have studied the low-temperature (T=6K) optical properties of a series of InGaN∕GaN single-quantum-well structures with varying indium fractions. With increasing indium fraction the peak emission moves to lower energy and the strength of the exciton–longitudinal-optical (LO)-phonon coupling increases. The Huang–Rhys factor extracted from the Fabry–Perot interference-free photoluminescence spectra has been compared with the results of a model calculation, yielding a value of approximately 2nm for the in-plane localization length scale of carriers. We have found reasonable agreement between this length scale and the in-plane extent of well-width fluctuations observed in scanning transmission electron microscopy high-angle annular dark-field images. High-resolution transmission electron microscopy images taken with a short exposure time and a low electron flux have not revealed any evidence of gross indium fluctuations within our InGaN quantum wells. These images could not, however, rule out the possible ...
208 citations
TL;DR: In this paper, the magnitude of the longitudinal electric field induced by both spontaneous and piezoelectric polarizations was determined by comparing experimental results with a variational calculation of excitonic energies and oscillator strengths.
Abstract: Continuous-wave, time-integrated, and time-resolved photoluminescence experiments are used to study the excitonic optical recombinations in wurtzite ZnO/Zn078Mg022O quantum wells of varying widths By comparing experimental results with a variational calculation of excitonic energies and oscillator strengths, we determine the magnitude (09MV∕cm) of the longitudinal electric field that is induced by both spontaneous and piezoelectric polarizations The quantum-confined Stark effect counteracts quantum confinement effects for well widths larger than 3nm, leading to emission energies that can lie 05eV below the ZnO excitonic gap and to radiative lifetimes that can be larger than milliseconds
206 citations
TL;DR: In this article, the InAs/InGaAs quantum dots-in-a-well (DWELL) infrared photodetectors are reviewed and some solutions for mitigating the low quantum efficiency are suggested at the end of this paper.
Abstract: Novel InAs/InGaAs quantum dots-in-a-well (DWELL) infrared photodetectors are reviewed. These detectors, in which the active region consists of InAs quantum dots (QDs) embedded in an InGaAs quantum well, represent a hybrid between a conventional quantum well infrared photodetector (QWIP) and a QD infrared photodetector (QDIP). Like QDIPs, DWELL detectors display normal incidence operation without gratings or optocouplers while demonstrating reproducible 'dial-in recipes' for control over the operating wavelength, like QWIPs. Using femtosecond spectroscopy, long carrier lifetimes have been observed in DWELL heterostructures, suggesting their potential for high temperature operation. Moreover, DWELL detectors have also demonstrated bias-tunability and multicolour operation in the mid-wave infrared (3–5 µm), long-wave infrared (LWIR, 8–12 µm) and very long-wave infrared (>14 µm) regimes. We have recently developed LWIR 320 × 256 focal plane arrays operating at liquid nitrogen temperatures. One of the potential problems with these detectors is the low quantum efficiency, which translates into low responsivity and detectivity. Some solutions for mitigating these problems are suggested at the end of this paper.
203 citations
TL;DR: In this article, the authors demonstrate an electrically pumped exciton-polariton emission, the first device in which strongly coupled states of light and matter are electrically excited.
Abstract: The strong coupling limit of cavity QED is reached when matter inserted inside a microcavity exchanges energy with the resonant mode of the cavity more rapidly than the combined rate at which light leaves the cavity and the matter wave function loses its phase information [1,2]. In this limit, the microcavity and matter form a composite quantum system with two new eigenstates that are superpositions of the initial uncoupled states, with new eigenenergies separated in energy by the Rabi splitting. The matter component of the coupled system can be a gas of atoms trapped inside the cavity [3], a superconducting qubit [4], or a solid state thin film containing excitons, in the form of an inorganic quantum well [5], quantum dot [6,7], or organic material [8], in which case the superposition states are referred to as exciton polaritons. Applications of strong coupling in atomic and semiconductor systems have led to one-atom zero threshold lasers [9], high gain polariton parametric amplifiers [10], and predictions that strong coupling may play a key role in future quantum information processors [11]. These experiments have all relied on optical pumping. Here we demonstrate electrically pumped exciton-polariton emission, the first device in which strongly coupled states of light and matter are electrically excited. The matter component of our device is a 6 � 1n mthick film of J aggregated dye. The film consists of 4 bilayers [12] of the cationic polyelectrolyte PDAC (poly diallyldimethylammonium chloride) and J aggregates of the anionic cyanine dye TDBC (5,6-dichloro-2-[3-[5,6-dichloro-1-ethyl-3-(3-sulfopropyl)-2(3H)-benzimidazolidene]-1-propenyl]-1-ethyl-3-(3-sulfopropyl) benzimidazolium hydroxide, inner salt, sodium salt), molecular structures shown in Fig. 1(a). The J aggregates are crystallites of dye in which the transition dipoles of the constituent molecules strongly couple to form a collective narrow linewidth optical transition possessing oscillator strength derived from all the aggregated monomers [13]. The bilayer films contain a high density of J aggregated TDBC and therefore have a very large peak absorption
201 citations
TL;DR: Analysis of the dephasing mechanisms reveals dipole selection rules closely analogous to those seen in atomic spectroscopy experiments, which suggest the prospects for exploiting them for scalable quantum information processing applications are more promising than previous dephase models would have predicted.
Abstract: Resonant optical coupling experiments have demonstrated coherent quantum interference between the Stark-split ``dressed states'' of a synthesized 3-level electronic system in a semiconductor quantum well. Analysis of the dephasing mechanisms reveals dipole selection rules closely analogous to those seen in atomic spectroscopy experiments. In this respect, these systems behave as ``artificial atoms'' for the purposes of observing a range of nonclassical coherent optical effects. The prospects for exploiting them for scalable quantum information processing applications are more promising than previous dephasing models would have predicted.
196 citations
TL;DR: In this article, the binding energy, longitudinal-transverse splitting energy, and exchange energy of 1s excitons have been determined to be 480, 70 and 31 meV, respectively.
Abstract: The electronic and excitonic structures of an inorganic–organic perovskite-type quantum-well crystal (C4H9NH3)2PbBr4 have been investigated by optical absorption, photoluminescence, electroabsorption, two-photon absorption, and magnetoabsorption spectroscopies. Excitons in (C4H9NH3)2PbBr4 are of the Wannier-type, and ns (n≥2) excitons form an ideal two-dimensional Wannier exciton system. The binding energy, longitudinal–transverse splitting energy, and exchange energy of 1s excitons have been determined to be 480, 70 and 31 meV, respectively. These high values originate from both a strong two-dimensional confinement and the image charge effect. These values are larger than those in (C6H13NH3)2PbI4, owing to the smaller dielectric constant of the well layer in (C4H9NH3)2PbBr4 than that in (C6H13NH3)2PbI4. The seemingly unusual electric-field dependence of excitons resonance is also reasonably understood by taking the image charge effect into account.
192 citations
TL;DR: The results suggest a direct experimental proof of this fundamental effect, confirming a long-standing theoretical prediction, and numerically and analytically find a resonance condition maximizing the zitterbewegung.
Abstract: We study the zitterbewegung of electronic wave packets in III-V zinc-blende semiconductor quantum wells due to spin-orbit coupling. Our results suggest a direct experimental proof of this fundamental effect, confirming a long-standing theoretical prediction. For electron motion in a harmonic quantum wire, we numerically and analytically find a resonance condition maximizing the zitterbewegung.
189 citations
Patent•
15 Apr 2005TL;DR: In this paper, the texturing in the region of the quantum well layers greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction.
Abstract: A semiconductor sensor, solar cell or emitter or a precursor therefore having a substrate and textured semiconductor layer deposited onto the substrate. The layer can be textured as grown on the substrate or textured by replicating a textured substrate surface. The substrate or first layer is then a template for growing and texturing other semiconductor layers from the device. The textured layers are replicated to the surface from the substrate to enhance light extraction or light absorption. Multiple quantum wells, comprising several barrier and quantum well layers, are deposited as alternating textured layers. The texturing in the region of the quantum well layers greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. This is the case in nitride semiconductors grown along the polar [0001] or [000-1] directions.
TL;DR: In this article, the experimental aspects of the optical properties of excitons in ZnO-based MQW heterostructures were discussed. And the binding energies of exciton and biexciton were enhanced from the bulk values, as a result of quantum-confinement effects.
Abstract: Recently the developments in the field of II?VI-oxides have been spectacular. Various epitaxial methods have been used to grow epitaxial ZnO layers. Not only epilayers but also sufficiently good-quality multiple quantum wells (MQWs) have been grown by laser molecular-beam epitaxy (laser-MBE). We mainly discuss the experimental aspect of the optical properties of excitons in ZnO-based MQW heterostructures. Systematic temperature-dependent studies of optical absorption and photoluminescence in these MQWs were used to evaluate the well-width dependence and the composition dependence of the major excitonic properties. Based on these data, the localization of excitons, the influence of exciton?phonon interaction and quantum-confined Stark effects are discussed. The optical spectra of dense excitonic systems are shown to be determined mainly by the interaction process between excitons and biexcitons. The high-density excitonic effects play a role in the observation of room-temperature stimulated emission in the ZnO MQWs. The binding energies of exciton and biexciton are enhanced from the bulk values, as a result of quantum-confinement effects.
TL;DR: Evidence of optical coupling between the two band gap emissions was observed and total photoluminescence quantum efficiency of the dual emitting bands reached as high as 30% at room temperature under synthetic conditions not optimized for high emission.
Abstract: Dual quantum systems, 0-dimensional quantum dot, and 2-dimensional quantum wells were constructed in one II-VI semiconductor nanocrystal by the epitaxial growth of a barrier (ZnS) layer between the systems in solution. By alteration of the thickness of the barrier layer, the two quantum systems were controlled to either electronically coupled or decoupled. Evidence of optical coupling between the two band gap emissions was also observed. The position and relative intensity of the two emissions can be independently tuned by reaction conditions. Total photoluminescence quantum efficiency of the dual emitting bands reached as high as 30% at room temperature under synthetic conditions not optimized for high emission.
Journal Article•
TL;DR: In this paper, the electronic structures of zero-dimensional quantum wells are studied with a spherical model in the framework of the effective mass theory, and the mixing effect of the heavy and light holes is taken into account, and symmetry classification and the energy levels of hole states are obtained.
Abstract: The electronic structures of zero-dimensional quantum wells are studied with a spherical model in the framework of the effective-mass theory. The mixing effect of the heavy and light holes is taken into account, and the symmetry classification and the energy levels of hole states are obtained. The energies of the donor and acceptor states are calculated. The difference between the shallow-impurity states and the eigenstates for the small semiconductor sphere disappears. The selection rules for the optical transition between the conduction- and valence-band states are obtained. The An =0 selection rule is not followed strictly because of the mixing of the L- and (L +2)-orbital wave functions in the wave functions of the hole states. The exciton binding energies are calculated for the small GaAs spheres. The energy levels of the ZnSe spheres are given as functions of the radius and compared with the experiments.
TL;DR: In this article, a tunnel injection quantum-dot laser is demonstrated, where self-organized quantum dots are p doped to optimize the gain, and the laser is characterized by Jth=180A∕cm2, T0=∞, dg∕dn≈1×10−14cm2.
Abstract: 1.3μm tunnel injection quantum-dot lasers are demonstrated. The laser heterostructures are grown by molecular-beam epitaxy. The InAs self-organized quantum dots are p doped to optimize the gain. The lasers are characterized by Jth=180A∕cm2, T0=∞, dg∕dn≈1×10−14cm2, f−3dB=11GHz, chirp of 0.1A, and zero α parameter.
TL;DR: In this paper, a two-color infrared focal plane array based on a voltage-tunable quantum dots-in-well (DWELL) design was demonstrated. But the active region consists of multiple layers of InAs quantum dots in an In0.15Ga0.85As quantum well.
Abstract: We report the demonstration of a two-color infrared focal plane array based on a voltage-tunable quantum dots-in-well (DWELL) design. The active region consists of multiple layers of InAs quantum dots in an In0.15Ga0.85As quantum well. Spectral response measurements yielded a peak at 5.5μm for lower biases and at 8–10μm for higher biases. Using calibrated blackbody measurements, the midwavelength and long wavelength specific detectivity (D*) were estimated to be 7.1×1010cmHz1∕2∕W(Vb=1.0V) and 2.6×1010cmHz1∕2∕W(Vb=2.6V) at 78 K, respectively. This material was processed into a 320×256 array and integrated with an Indigo 9705 readout chip and thermal imaging was achieved at 80 K.
TL;DR: In this paper, the authors present analytical expressions for internal electric field and strain in single and multiple quantum wells, incorporating electromechanical coupling, spontaneous polarization, and periodic boundary conditions.
Abstract: We present analytical expressions for internal electric field and strain in single and multiple quantum wells, incorporating electromechanical coupling, spontaneous polarization, and periodic boundary conditions. Internal fields are typically 2% lower than the fields calculated using an uncoupled model. We point out two possible interpolation routes to calculate the piezoelectric (PZ) constants eij of an alloy from the PZ constants of the constituent materials and show that, for an In0.2Ga0.8N∕GaN quantum well system, the respective internal electric fields differ by 10%. Using an effective-mass model, we explore the effect of the uncertainty in the elastic and PZ constants of GaN on the internal field and optical transitions of InGaN∕GaN quantum wells, and find that the range of published values of eij produces an uncertainty of more than ±20% in the internal field and of more than ±30% in the blueshift in optical transition energy between zero bias and flatband conditions (when the applied field is equa...
TL;DR: In this paper, a new barrier material for GaSb-based type-I laser diodes is introduced for wavelengths beyond 3μm, which improves the valence-band offset between GaInAsSb quantum wells and barriers.
Abstract: Quinternary AlGaInAsSb is introduced as a new barrier material for GaSb-based type-I laser diodes. For wavelengths beyond 3μm, this material improves the valence-band offset between GaInAsSb quantum wells and barriers as compared to standard GaInAsSb∕AlGaAsSb structures. The laser structures, which comprise three compressively strained GaInAsSb quantum wells and AlGaInAsSb barriers and waveguides, show good structural and optical quality. 3.26μm emission has been achieved with ridge waveguide lasers working in pulsed operation up to 50°C. With this emission wavelength, a strong absorption line of CH4 is accessible for gas absorption measurements.
TL;DR: In this article, the authors describe 1.1 and 1.3 µm p-doped tunnel injection self-organized In(Ga)As quantum dot (QD) laser emitting at 1.2 × 10−16 cm3.
Abstract: The modulation bandwidth of conventional 1.0–1.3 µm self-organized In(Ga)As quantum dot (QD) lasers is limited to ~6–8 GHz due to hot carrier effects arising from the predominant occupation of wetting layer/barrier states by the electrons injected into the active region at room temperature. Thermal broadening of holes in the valence band of QDs also limits the performance of the lasers. Tunnel injection and p-doping have been proposed as solutions to these problems. In this paper, we describe high-performance In(Ga)As undoped and p-doped tunnel injection self-organized QD lasers emitting at 1.1 and 1.3 µm. Undoped 1.1 µm tunnel injection lasers have ~22 GHz small-signal modulation bandwidth and a gain compression factor of 8.2 × 10−16 cm3. Higher modulation bandwidth (~25 GHz) and differential gain (3 × 10−14 cm2) are measured in 1.1 µm p-doped tunnel injection lasers with a characteristic temperature, T0, of 205 K in the temperature range 5–95°C. Temperature invariant threshold current (infinite T0) in the temperature range 5–75°C and 11 GHz modulation bandwidth are observed in 1.3 µm p-doped tunnel injection QD lasers with a differential gain of 8 × 10−15 cm2. The linewidth enhancement factor of the undoped 1.1 µm tunnel injection laser is ~0.73 at lasing peak and its dynamic chirp is <0.6 A at various frequencies and ac biases. Both 1.1 and 1.3 µm p-doped tunnel injection QD lasers exhibit zero linewidth enhancement factor (α ~0) and negligible chirp (< 0.2 A). These dynamic characteristics of QD lasers surpass those of equivalent quantum well lasers.
TL;DR: In this article, a grating-gated field effect transistor fabricated from a singlequantum well in a highmobility GaAs-AlGaAs heterostructure is shown to function as a continuously electrically tunable photodetector of terahertz radiation via excitation of resonant plasmon modes in the well.
Abstract: A grating-gated field-effect transistor fabricated from a single-quantum well in a high-mobility GaAs–AlGaAs heterostructure is shown to function as a continuously electrically tunable photodetector of terahertz radiation via excitation of resonant plasmon modes in the well. Different harmonics of the plasmon wave vector are mapped, showing different branches of the dispersion relation. As a function of temperature, the resonant response magnitude peaks at around 30K. Both photovoltaic and photoconductive responses have been observed under different incident power and bias conditions.
TL;DR: In this paper, a terahertz quantum-well photodetectors with background-limited infrared performance (BLIP) was reported. But the authors did not report the performance of the three different wavelengths.
Abstract: We report terahertz quantum-well photodetectors with background-limited infrared performance (BLIP). The device dark current characteristics were improved by employing thick barriers to reduce interwell tunneling. BLIP operations were observed for all samples (three in total) designed for different wavelengths. BLIP temperatures of 17, 13, and 12K were achieved for peak detection frequencies at 9.7THz (31μm), 5.4THz (56μm), and 3.2THz (93μm), respectively.
TL;DR: In this paper, the concept of below threshold and above threshold current injection efficiency of quantum well (QW) lasers is clarified and the analysis presented in this paper is applied to both the 1200nm and 1300nm emitting InGaAsN QW lasers.
Abstract: The concept of below-threshold and above-threshold current injection efficiency of quantum well (QW) lasers is clarified. The analysis presented here is applied to the current injection efficiency of 1200nm emitting InGaAs and 1300nm emitting InGaAsN QW lasers. The role of heavy-hole leakage in the InGaAsN QW lasers is shown to be significant in determining the device temperature sensitivity. The current injection efficiency of QW lasers with large monomolecular recombination processes is shown to be less temperature sensitive. Excellent agreement between theory and experiment is obtained for both the 1200nm emitting InGaAs QW and the 1300nm emitting InGaAsN QW lasers. Suppression of thermionic carrier escape processes in the InGaAsN QW results in high performance 1300nm emitting lasers operating up to high temperature.
TL;DR: In this paper, the optical rectification in a semiparabolic quantum well is theoretically investigated and the nonlinearity resulting from the asymmetry of the confining potential is studied in the lowest order.
Book•
01 Jan 2005TL;DR: Superlattice to Nanoelectronics, Second Edition as discussed by the authors, traces the history of the development of superlattices and quantum wells from their origins in 1969, including resonant tunneling via man-made quantum well states, optical properties and Raman scattering in manmade quantum systems, dielectric function and doping of a super-attice; and quantum step and activation energy.
Abstract: Superlattice to Nanoelectronics, Second Edition, traces the history of the development of superlattices and quantum wells from their origins in 1969. Topics discussed include the birth of the superlattice; resonant tunneling via man-made quantum well states; optical properties and Raman scattering in man-made quantum systems; dielectric function and doping of a superlattice; and quantum step and activation energy. The book also covers semiconductor atomic superlattice; Si quantum dots fabricated from annealing amorphous silicon; capacitance, dielectric constant, and doping quantum dots; porous silicon; and quantum impedance of electrons. * Written by one of the founders of this field* Delivers over 20% new material, including new research and new technological applications* Provides a basic understanding of the physics involved from first principles, while adding new depth, using basic mathematics and an explanation of the background essentials
TL;DR: In this paper, a specific growth procedure combining low-temperature growth of ZnMgO and postgrowth annealing at intermediate temperatures was proposed to deal with the large lattice misfit induced by the sapphire substrate.
Abstract: We report on a specific growth procedure combining low-temperature growth of ZnMgO and postgrowth annealing at intermediate temperatures. Despite the large lattice misfit induced by the sapphire substrate, layer-by-layer growth is accomplished up to the phase-separation limit found at a c-lattice constant of 0.5136nm and Mg mole fraction of 0.40. The procedure allows us to grow quantum wells with atomically smooth interfaces in a wide range of structural designs exhibiting prominent emission features up to room temperature.
TL;DR: In this paper, the authors have calculated band-edge energies for most combinations of zinc blende AlN, GaN, InN, N, GaP, GaAs, InP, InAs, GaSb, and InSb in which one material is strained to another.
Abstract: We have calculated band-edge energies for most combinations of zinc blende AlN, GaN, InN, GaP, GaAs, InP, InAs, GaSb, and InSb in which one material is strained to the other. Calculations were done for three different geometries (quantum wells, wires, and dots) and mean effective masses were computed in order to estimate confinement energies. For quantum wells, we have also calculated band-edges for ternary alloys. Energy gaps, including confinement, may be easily and accurately estimated using band energies and a simple effective mass approximation, yielding excellent agreement with experimental results. By calculating all material combinations we have identified interesting material combinations, such as artificial donors, that have not been experimentally realized. The calculations were perfomed using strain-dependent k center dot p theory and provide a comprehensive overview of band structures for strained heterostructures. (Less)
TL;DR: Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton, which may yield new applications for quantum well modulators in optical communications.
Abstract: Semiconductor quantum well electroabsorption modulators are widely used to modulate near-infrared (NIR) radiation at frequencies below 0.1 terahertz (THz). Here, the NIR absorption of undoped quantum wells was modulated by strong electric fields with frequencies between 1.5 and 3.9 THz. The THz field coupled two excited states (excitons) of the quantum wells, as manifested by a new THz frequency- and power-dependent NIR absorption line. Nonperturbative theory and experiment indicate that the THz field generated a coherent quantum superposition of an absorbing and a nonabsorbing exciton. This quantum coherence may yield new applications for quantum well modulators in optical communications.
TL;DR: In this article, a photoluminescence (PL) measurement revealed two emission peaks: one is position dependent and the other is not, and the position-dependent peak was attributed to emissions due to excitons confined in the ZnO well layer, while the position independent peak was caused by exciton in MgZnO barrier layers.
Abstract: ZnO∕MgZnO single quantum wells (QWs) in which the well width changes continuously were grown on sapphire (112¯0) substrates by metalorganic chemical vapor deposition. Photoluminescence (PL) measurement revealed two emission peaks: one is position dependent and the other is not. Polarized PL spectra obtained from cleaved facets demonstrated perfect two-dimensional features of the position-dependent emission peak. The position-dependent peak was attributed to emissions due to excitons confined in the ZnO well layer, and the position-independent peak was attributed to emissions due to excitons in MgZnO barrier layers. The width dependence of the emission energy from the ZnO QW was interpreted by a simple theoretical model. Typical PL decay time of the QW emission was 360ps at 77K. It was shorter than that of the MgZnO barrier, 470ps, due to the enhanced confinement effect in the QW.
TL;DR: In this paper, the nonlinear optical properties of quantum wells represented by a Poschl-Teller confining potential have been studied and the linear and the third-order non-linear optical intersubband absorption coefficients, the second-harmonic generation (SHG) susceptibility tensor, and optical rectification (OR) under the density matrix formalism are presented.
Abstract: The nonlinear optical properties of quantum wells (QWs) represented by a P\"oschl-Teller confining potential are studied. This potential is well suited for such purposes as it can easily become asymmetrical by a correct choice of its parameter set. We calculate the linear and the third-order nonlinear optical intersubband absorption coefficients, the second-harmonic generation (SHG) susceptibility tensor, and optical rectification (OR) under the density matrix formalism. Numerical results for a typical GaAs QW are presented. The resulting SHG and the OR coefficients are much larger than their values for bulk GaAs.
TL;DR: In this paper, room temperature photoluminescence at 1.6μm was demonstrated from InGaAs quantum dots capped with an 8nm GaAsSb quantum well.
Abstract: Room temperature photoluminescence at 1.6μm is demonstrated from InGaAs quantum dots capped with an 8nm GaAsSb quantum well. Results obtained from various sample structures are compared, including samples capped with GaAs. The observed redshift in GaAsSb capped samples is attributed to a type II band alignment and to a beneficial modification of growth kinetics during capping due to the presence of Sb. The sample structure is discussed on the basis of transmission electron microscopy results.