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[IEEE 2018 UKSim-AMSS 20th International Conference on Computer Modelling and Simulation (UKSim) - Cambridge, United Kingdom (2018.3.27-2018.3.29)] 2018 UKSim-AMSS 20th International Conference on Computer Modelling and Simulation (UKSim) - A Multiple Quantum Well Structure Simulator
摘要： A simulator was developed for modeling and designing multiple quantum wells structures such as quantum well infrared photodetectors and quantum cascade laser, based on a single-electron effective mass Schr?dinger equation. It employs box integration finite differences and transfer matrix approaches to find energies of bound and scattering states in the structures. The graphical user interface allows the user to vary easily design parameters including effective mass, layer thickness and number of layers as well as simulation parameters in order to optimize the structure for different device applications and functionality. Three simulation examples were performed on: three coupled quantum wells infrared two-color asymmetric quantum well structure, photodetector structure and on a quantum cascade laser design. The results show an accuracy which is comparable to more complicated simulations.
关键词： Effective mass approximation,TMM,Multiple Quantum Wells Structures,FDM
更新于2025-09-23 15:22:29
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Characteristics of GeSn-based multiple quantum well heterojunction phototransistors: a simulation-based analysis
摘要： Introduction of multiple quantum wells (MQWs) is an efficient way to enhance the light absorption capability in phototransistors. Direct band gap Ge1?xSnx alloy (x?>?0.08) having large absorption coefficient is an attractive material for heterojunction phototransistors (HPTs) compatible with CMOS platform. In this work, simulations are employed to obtain current gain, responsivity and collector current characteristics of Ge/GeSn/Ge HPTs with incorporation of MQWs (Ge0.87Sn0.13/Ge0.83Sn0.17) in the base region. The performances of bulk, single quantum well and MQW HPT structures are examined and compared. Best performance is shown by HPTs having MQW structure over a wide range of base emitter voltage.
关键词： simulation,current gain,heterojunction phototransistors,responsivity,GeSn,multiple quantum wells
更新于2025-09-23 15:21:21
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Low-Voltage, Coupled Multiple Quantum Well Electroreflective Modulators towards Ultralow Power Inter-Chip Optical Interconnects
摘要： An electroreflective modulator based on multiple-pass electroabsorption (EA) of coupled multiple quantum wells (CMQWs) is demonstrated for integration with low-loss polymer optical waveguides towards inter-chip and on-board optical interconnects at 850 nm. Taking advantage of coupling between quantum states in MQWs, the top polymer cladding and the bottom Au mirror form a Fabry-Pérot cavity to further enhance the EA of CMQWs, thereby greatly improving the extinction ratio (ER) at a low voltage. The device achieves an ER of ~6 dB and an insertion loss (IL) <3 dB at 2 V, notably outperforming conventional surface-incident EA modulators at the same driving voltage. A further optimized modulator design can achieve a peak ER of 9-12 dB at 2V with a low IL of 2-3 dB and a relatively broad spectral bandwidth of ~10 nm. The low capacitance and reverse bias operation at a low voltage potentially offer ~10× lower power consumption compared to direct modulation of 850 nm lasers. This simple surface-incident CMQW modulator is a promising candidate for integration with ultralow power inter-chip and on-board interconnect architectures.
关键词： Modulator,Coupled Multiple Quantum Wells,Optical Interconnect,Fabry-Perot cavity,Electroabsorption
更新于2025-09-23 15:21:01
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Reducing stimulated emission threshold power density of AlGaN/AlN multiple quantum wells by nano-trench-patterned AlN template
摘要： We investigate the crystal quality of epitaxy lateral overgrowth (ELOG) AlN layers and the performance of optical pumping AlGaN-based deep-ultraviolet (DUV) laser diodes (LDs) on two different patterned AlN templates upon sapphire substrate. The full width at half maximum values of (0002) and (10 1(cid:2)2) X-ray diffraction rocking curves of the ELOG AlN layer on the nano-net-patterned AlN template are 76 and 306 arcsec, and the values of that on the nano-trench-patterned AlN template are 114 and 357 arcsec, respectively. Nevertheless, the threshold power density (Pth) of the 272-nm lasing from the multiple quantum wells (MQWs) on the nano-trench-patterned AlN template is 11% lower than that on the nano-net-patterned AlN template. The reason is that the continuous low threading dislocation density (TDD) MQWs zones above the ELOG coalescent areas upon trenched patterns are in parallel with the stimulated light emission direction. When light resonates through the continuous low TDD MQWs zones, it has higher optical gain and less non-radiative recombination than the case on the nano-net-patterned AlN template where the low TDD MQWs zones are discontinuous on the light path. The results indicate that not only the crystal quality but also the TDD distribution originated from the ELOG on the patterned templates have crucial influence on the Pth, and trench-patterned template can improve the performance of waveguide LDs with Fabry-Perot cavities.
关键词： laser diode,deep ultraviolet,multiple quantum wells,AlGaN,AlN
更新于2025-09-23 15:21:01
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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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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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[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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Effect of Indium Composition on the Microstructural Properties and Performance of InGaN/GaN MQWs Solar Cells
摘要： In the present work, InGaN/GaN multiple quantum wells (MQWs) solar cells with different concentrations of indium have been investigated in-depth. It was demonstrated that applying a medium-high indium content (about 28%) does not facilitate solar cell photoelectric conversion efficiency due to the increase of edge dislocations. Moreover, the effects of different indium contents on InGaN/GaN MQWs solar cells were investigated and was revealed, that the short-circuit current density and photoelectric conversion efficiency are improved with the increase of indium contents. However, they show a noticeable reduction in the indium content of 28%. Furthermore, the optical properties and the behaviour of the microstructure defects were analysed. It was also demonstrated that the number of edge dislocations acted as non-radiation recombination centers increasing rapidly when the indium content reaches 28%, playing a key role in decreasing the active number of photon-generated carriers. As a result, the short-circuit current density and photoelectric conversion efficiency decrease obviously for an indium content of 28%. This work can provide insight into the origin of the degradation of these structures and the improvement of device design with medium-high indium contents.
关键词： solar cells.,InGaN/GaN multiple quantum wells (MQWs),microstructure and performance,Indium composition
更新于2025-09-12 10:27:22