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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Terahertz Detectors Based on Plasmonic Excitations in Double CdTe/CdMgTe Quantum Wells
摘要： Double CdTe/CdMgTe quantum wells modulation doped with Iodine were etched to fabricate grids with a period of 8 μm and a geometrical aspect ratio ((cid:2)) between 0.2 and 0.7. Etching removed only the well closer to the sample's surface. Transmission of terahertz radiation as a function of magnetic field (B) up to 10 T was measured at 2 K. The spectra show a single magnetoplasmon resonance (MPR) which position in B depends on (cid:2). A huge amplitude of MPR, comparable to that of the cyclotron resonance, allows us to propose such structures as tunable plasmonic terahertz detectors.
关键词： CdTe/CdMgTe quantum wells,terahertz detectors,plasmonic excitations,magnetoplasmon resonance
更新于2025-09-16 10:30:52
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Improving Output Power of InGaN Laser Diode Using Asymmetric In0.15Ga0.85N/In0.02Ga0.98N Multiple Quantum Wells
摘要： Herein, the optical ?eld distribution and electrical property improvements of the InGaN laser diode with an emission wavelength around 416 nm are theoretically investigated by adjusting the relative thickness of the ?rst or last barrier layer in the three In0.15Ga0.85N/In0.02Ga0.98N quantum wells, which is achieved with the simulation program Crosslight. It was found that the thickness of the ?rst or last InGaN barrier has strong e?ects on the threshold currents and output powers of the laser diodes. The optimal thickness of the ?rst quantum barrier layer (FQB) and last quantum barrier layer (LQB) were found to be 225 nm and 300 nm, respectively. The thickness of LQB layer predominantly a?ects the output power compared to that of the FQB layer, and the highest output power achieved 3.87 times that of the reference structure (symmetric quantum well), which is attributed to reduced optical absorption loss as well as the reduced vertical electron leakage current leaking from the quantum wells to the p-type region. Our result proves that an appropriate LQB layer thickness is advantageous for achieving low threshold current and high output power lasers.
关键词： asymmetric multiple quantum wells,optical absorption loss,InGaN laser diodes,barrier thickness,electron leakage current
更新于2025-09-16 10:30:52
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Type-II AlInN/ZnGeN <sub/>2</sub> quantum wells for ultraviolet laser diodes
摘要： We propose a type-II AlInN/ZnGeN2 quantum well (QW) structure serving as the active region for ultraviolet (UV) laser diodes. A remarkably low threshold current density can be achieved using the type-II AlInN/ZnGeN2 QW structure, providing a pathway for the realization of electrically-driven nitride-based semiconductor UV laser diodes. ZnGeN2 has both a very similar lattice constant and bandgap to GaN. Its large band offsets with GaN enable the potential of serving as a hole confinement layer to increase the electron-hole wavefunction overlap in the active region. In this study, we investigate the spontaneous emission and gain properties of type-II AlInN/ZnGeN2 QWs with different ZnGeN2 layer thicknesses. Our findings show that the use of ZnGeN2 layers in the active region provides a significant improvement in hole carrier confinement, which results in ～5 times enhancement of the electron-hole wave function overlap. Such an enhancement provides the ability to achieve a significant increase (～6 times) in the spontaneous emission rate and material gain, along with a remarkable reduction in threshold carrier density compared to the conventional AlGaN-based QW design, which is essential for practical UV laser diodes.
关键词： ultraviolet laser diodes,material gain,AlInN/ZnGeN2,Type-II quantum wells,spontaneous emission
更新于2025-09-16 10:30:52
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Two-dimensional analysis of the nonuniform quantum yields of multiple quantum wells for AlGaN-based deep-ultraviolet LEDs grown on AlN templates with dense macrosteps using cathodoluminescence spectroscopy
摘要： AlGaN-based deep-ultraviolet light-emitting diodes (LEDs) incorporating uneven multiple quantum wells (MQWs) with inclined and terrace zones, which were fabricated on an AlN template with dense macrosteps, have exhibited a high internal quantum efficiency (IQE). To investigate the microscopic structure of uneven MQWs, cathodoluminescence (CL) mapping characterization was carried out, and the maps of the CL intensity at 300 K relative to that at 38 K were obtained for uneven MQWs that targeted 265 and 285 nm LEDs. At an electron beam current of less than 1.0 nA, the signals from inclined and terrace zones of the uneven MQWs were confirmed to satisfy the non-saturated excitation condition at 300 K. Nonradiative recombination (NR) was insufficiently frozen even at 38 K, specifically on the terraces in the 265 nm MQW, suggesting high concentrations of NR centers due to point defects (PDs). In contrast, NR in the 285 nm MQW at 38 K was closer to freeze-out. The concentration of PDs in the 285 nm MQW was likely to be lower than that in the 265 nm MQW. Finally, the ratios of the CL intensity at 300 K to those at 38 K were mapped, demonstrating an approach to creating an approximate map of IQE. The values in the CL intensity ratio maps are discussed by considering the analytical error factors. The results support the model of localized current injection through Ga-rich stripe zones in the n-AlGaN cladding layer.
关键词： AlGaN,cathodoluminescence spectroscopy,internal quantum efficiency,deep-ultraviolet LEDs,multiple quantum wells
更新于2025-09-12 10:27:22
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Electrically tuning many-body states in a Coulomb-coupled InAs/InGaSb double layer
摘要： We study the transport properties of an electron-hole double layer consisting of barrier-separated InAs/InGaSb quantum wells. We focus on measurements of four-terminal resistivity of a Hall-bar sample as a function of electron (n) and hole (p) density, that are being tuned by a pair of top and bottom gates. In zero magnetic ?eld, we clearly observe an insulating phase which occurs at a charge neutral point, below a critical carrier density n = p < 1 × 1011 cm?2. This phase is characterized by a narrow and thermally activated resistance peak and an anomalous Hall resistance. This observation reinforces our previous ?nding of an excitonic insulator. Remarkably, when the layer densities are being tuned into imbalance, here p (cid:2) n, a broader resistance peak emerges. We discuss this phase with respect to a possible (theoretically predicted) charge density wave ground state. Both phases can persist above ～25 K, indicating robust correlations in the electron-hole double layers.
关键词： electron-hole double layer,exciton condensation,InAs/InGaSb quantum wells,quantum spin Hall effect,charge density wave
更新于2025-09-12 10:27:22
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Numerical Demonstration of Trade-off between Carrier Confinement Effect and Carrier Transport for Multiple-Quantum-Well Based High-efficiency InGaP Solar Cells
摘要： To promote InGaP solar cell efficiency toward the theoretical limit, one promising approach is to incorporate multiple quantum wells (MQWs) into the InGaP host and improve its open-circuit voltage by facilitating radiative carrier recombination owing to carrier confinement. In this research, we demonstrate numerically that a strain-balanced (SB) In1-xGaxP/In1-yGayP MQW enhances confined carrier density while degrades the effective carrier mobility. However, a smart design of the MQW structure is possible by considering quantitatively the trade-off between carrier confinement effect and carrier transport, and MQW can be advantageous over the InGaP bulk material for boosting photovoltaic efficiency.
关键词： InGaP,carrier confinement effect,photovoltaics,multiple quantum wells
更新于2025-09-12 10:27:22
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Coupled Quantum Wells
摘要： Intersubband transitions in ZnO material systems are predicted to be promising candidates for infrared and terahertz (THz) optoelectronic devices due to their unusual material properties. In particular, the temperature performance of THz quantum cascade lasers is postulated to be significantly enhanced using ZnO material systems due to their large optical phonon energy. Taking a step forward toward that goal, intersubband transitions in ZnO/MgxZn1?xO asymmetric coupled quantum wells are observed on a nonpolar m plane ZnO substrate. Two absorption peaks are observed in the energy range from approximately 250 meV to approximately 410 meV at room temperature, unambiguously demonstrating the interwell coupling in the asymmetric coupled quantum wells. A theoretical model taking into account the interaction between intersubband transitions shows reasonable overall agreement with the experimental results, thus proving the strong coupling nature of the investigated system. As the building block of complex quantum structures based on intersubband transitions, the results presented show great potential applications of ZnO/MgxZn1?xO material systems in infrared and THz optoelectronics and physics.
关键词： intersubband transitions,ZnO,optoelectronics,quantum wells,THz,infrared
更新于2025-09-12 10:27:22
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Deep UV laser at 249 nm based on GaN quantum wells
摘要： In this letter, we report on deep UV laser emitting at 249 nm based on thin GaN quantum wells (QWs) by optical pumping at room temperature. The laser threshold was 190 kW/cm2 that is comparable to state-of-the-art AlGaN QW lasers at similar wavelengths. The laser structure was pseudomorphically grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition, comprising 40 pairs of 4 monolayer (ML) GaN QWs sandwiched by 6 ML AlN quantum barriers (QBs). The low threshold at the wavelength was attributed to large optical and quantum confinement, and high quality of the material, interface, and Fabry-P?rot facet. The emissions below and above the threshold were both dominated by transverse electric polarizations thanks to the valence band characteristics of GaN. This work unambiguously demonstrates the potentials of the binary AlN/GaN heterojunctions for high-performance UV emitters.
关键词： GaN quantum wells,deep UV laser,UV emitters,AlN/GaN heterojunctions,optical pumping
更新于2025-09-12 10:27:22
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Monolithic integration of VCSEL and coupled cavity RCEPD for short-reach single-fiber bi-directional optical interconnects
摘要： In this paper, we propose a monolithic integration of vertical-cavity surface-emitting laser (VCSEL) and coupled cavity resonant cavity enhancement photodiode (ccRCEPD). Based on this structure, a couple of matched chips is designed for single fiber bidirectional optical interconnects. That type of integration can easily put VCSEL and (photodiode) PD into one package, which not only reduces the costs of the device packages and even cut the costs of the optical system like beam splitter, but also can save the space in optical transceiver to make it tight. These chips’ VCSELs show a threshold current of 1.6 mA and 1.7 mA, and a slope efficiency of 0.74 W/A and 0.97 W/A. VCSELs’ modulation bandwidth is 9.5 GHz and 11.0 GHz, and PDs’ response bandwidth is 10 GHz. Furthermore, the modulation bandwidth can be higher if the material of the multiple quantum wells (MQWs) is transformed GaAs/AlGaAs to InGaAs/AlGaAs. And by optimizing, the 3dB bandwidth of PD will be higher.
关键词： ccRCEPD,bidirectional optical interconnects,VCSEL,monolithic integration,quantum wells
更新于2025-09-12 10:27:22
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High-performance flat-type InGaN-based light-emitting diodes with local breakdown conductive channel
摘要： Flat-type InGaN-based light-emitting diodes (LEDs) without an n-type contact electrode were developed by using a local breakdown conductive channel (LBCC), and the effect of the In content of the InGaN quantum wells (QWs) on the local breakdown phenomenon was investigated. Electroluminescence and X-ray analyses demonstrated that the homogeneity and crystallinity of the InGaN QWs deteriorated as the In content of the InGaN QWs increased, thereby increasing the reverse leakage current and decreasing the breakdown voltage. After reverse breakdown with a reverse current of several mA, an LBCC was formed on the GaN-based LEDs. The surface size and anisotropic shape of the LBCC increased as the indium content of the InGaN QWs in the LEDs increased. Moreover, a flat-type InGaN LED without an n-type electrode was developed by using the LBCC. Notably, the resistance of the LBCC decreased with increasing indium content in the InGaN QWs, leading to lower resistance and higher light emission of the flat-type InGaN-based LEDs without an n-type contact electrode.
关键词： light-emitting diodes,reverse leakage current,quantum wells,breakdown voltage,InGaN,local breakdown conductive channel
更新于2025-09-12 10:27:22