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Polarization-Sensitive Fourier-Transform Spectroscopy of HgTe/CdHgTe Quantum Wells in the Far Infrared Range in a Magnetic Field
摘要： Spectra of magnetoabsorption and Faraday rotation in HgTe/CdHgTe heterostructures with single and double quantum wells in high magnetic fields up to 11 T have been studied by the Fourier-transform spectroscopy method. The study of Faraday rotation spectra makes it possible to determine the sign of resonance circular polarization of transitions between Landau levels of carriers, which allows identifying observed intraband and interband transitions in the far and middle infrared ranges.
关键词： Faraday rotation,Landau levels,magnetoabsorption,Fourier-transform spectroscopy,HgTe/CdHgTe quantum wells
更新于2025-09-10 09:29:36
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Hydrostatic and uniaxial effects in InGaN/GaN quantum wells
摘要： We calculate strains, polarizations, and electric fields in InGaN/GaN quantum wells (lattice matched to GaN) under the influence of hydrostatic and uniaxial (along the c-axis) pressure. We calculate the confinement energies for electrons and holes, and we derive simple expressions for the transition energies and their pressure derivatives. We include the changes of the dielectric constant with pressure. The results seem compatible with the experimental data.
关键词： confinement energies,transition energies,uniaxial pressure,electric fields,strain,InGaN/GaN quantum wells,polarization,hydrostatic pressure
更新于2025-09-10 09:29:36
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Quantum Hall stripes in high-density GaAs/AlGaAs quantum wells
摘要： We report on quantum Hall stripes (QHSs) formed in higher Landau levels of GaAs/AlGaAs quantum wells with high carrier density (ne > 4 × 1011 cm?2) which is expected to favor QHS orientation along the unconventional (cid:2)1ˉ10(cid:3) crystal axis and along the in-plane magnetic ?eld B(cid:4). Surprisingly, we ?nd that at B(cid:4) = 0 QHSs in our samples are aligned along the (cid:2)110(cid:3) direction and can be reoriented only perpendicular to B(cid:4). These ?ndings suggest that high density alone is not a decisive factor for either abnormal native QHS orientation or alignment with respect to B(cid:4), while quantum con?nement of the 2DEG likely plays an important role.
关键词： quantum confinement,high carrier density,in-plane magnetic field,quantum Hall stripes,GaAs/AlGaAs quantum wells
更新于2025-09-09 09:28:46
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Nonreciprocal Optical and Magnetooptical Effects in Semiconductor Quantum Wells
摘要： Effects implying violation of the Fresnel light reflection laws in semiconductor structures with quantum wells (QWs) have been investigated. This violation is related to the manifestation of spatial dispersion caused by spin–orbit coupling in structures without inversion centers. The spin–orbit coupling constants characterizing polarization conversion in symmetric and asymmetric structures with QWs have been measured.
关键词： spatial dispersion,nonreciprocal optical effects,polarization conversion,spin–orbit coupling,semiconductor quantum wells,magnetooptical effects
更新于2025-09-09 09:28:46
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Thermopower of a Two-Dimensional Semimetal in a HgTe Quantum Well
摘要： The thermopower in a two-dimensional semimetal existing in HgTe quantum wells 18–21 nm thick has been studied experimentally and theoretically for the first time. It has been found theoretically and experimentally that the thermopower has two components—diffusion and phonon-drag—and that the second component is several times larger than the first. It has been concluded that the electron–hole scattering plays an important role in both mechanisms of the thermopower.
关键词： diffusion,thermopower,HgTe quantum wells,two-dimensional semimetal,phonon-drag,electron–hole scattering
更新于2025-09-09 09:28:46
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Influence of the Quantum Well Structure and Growth Temperature on a Five-Layer InGaMnAs Quantum Well with an InGaAs Buffer Layer
摘要： The in?uence of quantum well structure and growth temperature on a synthesized multilayer system composed of a ?ve-layer InMnGaAs quantum well with an InGaAs buffer layer grown on semi-insulating (100)-oriented substrates prepared by low temperature molecular beam epitaxy was studied. The magnetization measurements using a superconducting quantum interference device indicated the existence of ferromagnetism with a Curie temperature above room temperature in the ?ve-layer InGaMnAs quantum well structure with an InGaAs buffer layer in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements con?rmed the second phase formation of ferromagnetic GaMn clusters. The ferromagnetism that exists in the ?ve-layer of the InMnGaAs quantum well with the InGaAs buffer layer results from a superposition of the ferromagnetism of the low temperature region from the substitutional Mn ions into Ga sites or interstitial Mn ions as well as the presence of manganese ions dopant clusters such as GaMn clusters.
关键词： Molecular Beam Epitaxy,Clusters,Ferromagnetism,Quantum Wells
更新于2025-09-09 09:28:46
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Synthesis and photoluminescence properties of hexagonal BGaN alloys and quantum wells
摘要： Hexagonal boron nitride (h-BN) has emerged as an important extreme bandgap semiconductor as well as a two-dimensional material. Achieving the ability for tuning the optoelectronic properties through alloying and heterojunction will further expand the applications of h-BN. By utilizing h-BN epilayer as a template, the synthesis of BN-rich B1?xGaxN alloys and quantum wells crystalized in the hexagonal phase has been demonstrated for the first time by metal organic chemical vapor deposition. The incorporation of Ga tends to enhance the conductivity. A blue shift in the band-edge emission upon the formation of h-BN/BGaN/BN QW has been observed, indicating the feasibility for heterojunction formation.
关键词： hexagonal boron nitride,MOCVD,photoluminescence,BGaN alloys,quantum wells
更新于2025-09-09 09:28:46
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Short infrared wavelength quantum cascade detectors based on m-plane ZnO/ZnMgO quantum wells
摘要： This paper reports on the demonstration of quantum cascade detectors (QCDs) based on ZnO/ZnMgO quantum wells (QWs) grown by molecular beam epitaxy on an m-plane ZnO substrate. The TM-polarized intersubband absorption is peaked at a 3 lm wavelength. The sample has been processed in the form of square mesas with sizes ranging from 10 (cid:2) 10 lm2 up to 100 (cid:2) 100 lm2. The I-V characteristics reveal that 86% of the 260 devices are operational and that the surface leakage current is negligible at room temperature, which is not the case at 77 K. The photocurrent spectroscopy of 100 (cid:2) 100 lm2 QCDs reveals a photocurrent resonance at a 2.8 lm wavelength, i.e., slightly blue-shifted with respect to the intersubband absorption peak. The photocurrent persists up to room temperature. The calibrated peak responsivity amounts to 0.15 mA/W under irradiation at Brewster’s angle of incidence. This value allows us to estimate the transfer ef?ciency (1.15%) of the photoexcited electrons into the active QW of the next period.
关键词： quantum cascade detectors,m-plane ZnO substrate,intersubband absorption,ZnO/ZnMgO quantum wells,photocurrent spectroscopy
更新于2025-09-04 15:30:14
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High-efficiency electron-beam-pumped sub-240-nm ultraviolet emitters based on ultra-thin GaN/AlN multiple quantum wells grown by plasma-assisted molecular-beam epitaxy on <i>c</i> -Al <sub/>2</sub> O <sub/>3</sub>
摘要： We report the internal structures and emission properties of GaN/AlN single- and multiple-quantum-well (QW) heterostructures with well widths of dw = 1–4 monolayers (MLs), grown by plasma-assisted molecular-beam epitaxy on c-sapphire at metal-rich conditions and low temperatures (>700 °C). The formation of plane QWs with abrupt symmetrical interfaces is con?rmed by both scanning transmission electron microscopy and X-ray di?raction analysis. Pulse-scanning and continuous-wave output powers of 150 and 28 mW, respectively, at a peak emission wavelength of 235 nm were achieved at 300 K in an electron-beam-pumped deep-ultraviolet (1.5 ML-GaN/5.5 nm-AlN)360 multiple-QW emitter with a maximum e?ciency of 0.75%.
关键词： plasma-assisted molecular-beam epitaxy,electron-beam-pumped,deep-ultraviolet emitters,GaN/AlN,quantum wells
更新于2025-09-04 15:30:14
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Strong suppression of In desorption from InGaN QW by improved technology of upper InGaN/GaN QW interface
摘要： The aim of this work is to elucidate how di?erent growth mode and composition of barriers can in?uence the QW properties and their PL and to ?nd optimal QW capping process, to suppress the In desorption from QWs and to maintain the QW PL e?ciency. It concentrates on the technology procedure for growth of upper quantum well (QW) interfaces in InGaN/GaN QW structure when di?erent temperature for QW and barrier epitaxy is used. We have found that optimal photoluminescence (PL) results were achieved, when the growth after QW formation was not interrupted, but immediately continued during the temperature ramp by the growth of (In)GaN capping layer with small introduction of In precursor into the reactor. Optimal barrier between QW with respect to PL results was found to be pure GaN. We have shown according to SIMS and HRTEM results that by this technological procedure the InGaN desorption was considerably suppressed and three times higher In concentration and two times thicker QWs were achieved for the same QW growth parameters without deterioration of PL intensity in comparison to sample with usually used thin GaN low temperature capping protection. Additionally, for samples covered by the QW capping layer during the temperature ramp the defect band is almost completely missing, thus we can conclude that this defect band is connected with quality of the upper QW interface.
关键词： A1. Interfaces,A3. Quantum wells,B1. Nitrides,A3. MOVPE,B2. Scintillators
更新于2025-09-04 15:30:14