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- 2018
- differential low noise amplifier
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[IEEE 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Sao Paulo, Brazil (2019.8.26-2019.8.30)] 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - High-Efficiency GaAs Solar Cell Optimization by Theoretical Simulation
摘要： Theoretical simulations of solar cell current-voltage characteristics provide important information for a better design of the device structure, such as layers thicknesses and doping levels, in order to obtain high photovoltaic conversion efficiency. The inclusion of precise material parameters is critical to obtain reliable results and detailed understanding of the simulated device operation. In this study, GaAs solar cell structures were simulated by drift-diffusion model with SCAPS-1D in order to optimize the performance under 1 sun illumination. Moreover, we used the published results of some devices as references to infer their structures, as the details are normally not completely disclosed by the authors. To do so, an optimization study was required to probe different materials, thicknesses and doping levels for the layers. With the inferred structure, it was possible to evaluate the possibility of improvements through variation of the structure parameters to achieve even higher efficiencies.
关键词： Theoretical Simulation,Optimization,GaAs Solar Cell,SCAPS-1D
更新于2025-09-12 10:27:22
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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) - Tail-Suppressed THz Photocurrent by a Bi-Polar Photoconductive Antenna Fabricated on Semi-insulating GaAs
摘要： We designed and fabricated a bi-polar type photoconductive antenna (PCA) for efficient generation of broadband terahertz (THz) radiation. The falling time of overlyingly generated photocurrent from bi-polar PCA can achieve 200 fs via superimposing two primarily opposite polarity photocurrent pulses having falling time of 100 ps with time delay of 200 fs. The simulation results disclosed a possibility to shift the central frequency from 0.1 to 1.3 THz and enhance the THz power by twice in the range 1.5 - 3.3 THz by using low cost substrate with long carrier life time such as semi-insulating gallium arsenide (SI-GaAs).
关键词： photocurrent,terahertz radiation,bi-polar photoconductive antenna,SI-GaAs
更新于2025-09-12 10:27:22
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Optical properties of InAs quantum Dots/GaAs waveguides for ultra-fast scintillators
摘要： InAs Quantum Dots (QDs) embedded in a GaAs matrix have unique scintillation properties, valuable for high-energy physics and medical applications. Temperature-dependent photoluminescence, waveguide attenuation and alpha particle response measurements were employed to analyze the optical properties of a 25 m m thick waveguiding scintillator. Optimizing the electrostatics of the QD layered structure with p-type modulation doping resulted in QD photoluminescence (PL) efficiency as high as 60% at room temperature. Analysis of attenuation of the QD waveguide showed surface scattering predominated over the first 2-3 mm of light propagation and low (~1 cm-1) self-absorption was more significant at longer distances, after the after the decay of high order modes (high angle light rays). Responses to 5.5 MeV alpha particles from the integrated photodiode on top of the QD scintillator/waveguide (QD/WG) show an extremely fast (300 ps) decay constant, and a 70 ps time resolution (limited by circuit noise and bandwidth) with a collection efficiency of 17000 photons per 1 MeV of deposited energy.
关键词： InAs Quantum Dots,GaAs waveguides,ultra-fast scintillators,alpha particle response,photoluminescence
更新于2025-09-12 10:27:22
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Wide‐Bandgap Perovskite/Gallium Arsenide Tandem Solar Cells
摘要： Gallium arsenide (GaAs) photovoltaic (PV) cells have been widely investigated due to their merits such as thin-film feasibility, flexibility, and high efficiency. To further increase their performance, a wider bandgap PV structure such as indium gallium phosphide (InGaP) has been integrated in two-terminal (2T) tandem configuration. However, it increases the overall fabrication cost, complicated tunnel-junction diode connecting subcells are inevitable, and materials are limited by lattice matching. Here, high-efficiency and stable wide-bandgap perovskite PVs having comparable bandgap to InGaP (1.8–1.9 eV) are developed, which can be stable low-cost add-on layers to further enhance the performance of GaAs PVs as tandem configurations by showing an efficiency improvement from 21.68% to 24.27% (2T configuration) and 25.19% (4T configuration). This approach is also feasible for thin-film GaAs PV, essential to reduce its fabrication cost for commercialization, with performance increasing from 21.85% to 24.32% and superior flexibility (1000 times bending) in a tandem configuration. Additionally, potential routes to over 30% stable perovskite/GaAs tandems, comparable to InGaP/GaAs with lower cost, are considered. This work can be an initial step to reach the objective of improving the usability of GaAs PV technology with enhanced performance for applications for which lightness and flexibility are crucial, without a significant additional cost increase.
关键词： gallium arsenide,phase segregation,perovskite/GaAs tandem cells,thin-film flexible tandem cells,wide-bandgap perovskites
更新于2025-09-12 10:27:22
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A facile light‐trapping approach for ultrathin GaAs solar cells using wet chemical etching
摘要： Thinning down the absorber layer of GaAs solar cells can reduce their cost and improve their radiation hardness, which is important for space applications. However, the lighttrapping schemes necessary to achieve high absorptance in these cells can be experimentally challenging or introduce various parasitic losses. In this work, a facile lighttrapping approach based on wet chemical etching is demonstrated. The rear‐side contact layer of ultrathin GaAs solar cells is wet‐chemically textured in between local Ohmic contact points using an NaOH‐based etchant. The resulting contact layer morphology is characterized using atomic force microscopy and scanning electron miscroscopy. High broadband diffuse reflectance and haze factors are measured on bare and Ag‐coated textured contact layers. The textured contact layer is successfully integrated as a diffusive rear mirror in thin‐film solar cells comprising a 300‐nm GaAs absorber and Ag rear contact. Consistent increases in short‐circuit current density (JSC) of approximately 3 mA cm?2 (15%) are achieved in the textured cells, while the open‐circuit voltages and fill factors do not suffer from the textured rear mirror. The best cell achieves a JSC of 24.8 mA cm?2 and a power conversion efficiency of 21.4%. The textured rear mirror enhances outcoupling of luminescence at open circuit, leading to a strong increase in the external luminescent efficiency.
关键词： ultra‐thin GaAs,wet etching,textured III‐V solar cells,light trapping,luminescence outcoupling
更新于2025-09-12 10:27:22
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Electrically tunable effective g-factor of a single hole in a lateral GaAs/AlGaAs quantum dot
摘要： Electrical tunability of the g-factor of a confined spin is a long-time goal of the spin qubit field. Here we utilize the electric dipole spin resonance (EDSR) to demonstrate it in a gated GaAs double-dot device confining a hole. This tunability is a consequence of the strong spin-orbit interaction (SOI) in the GaAs valence band. The SOI enables a spin-flip interdot tunneling, which, in combination with the simple spin-conserving charge transport leads to the formation of tunable hybrid spin-orbit molecular states. EDSR is used to demonstrate that the gap separating the two lowest energy states changes its character from a charge-like to a spin-like excitation as a function of interdot detuning or magnetic field. In the spin-like regime, the gap can be characterized by the effective g-factor, which differs from the bulk value owing to spin-charge hybridization, and can be tuned smoothly and sensitively by gate voltages.
关键词： g-factor,spin qubit,electric dipole spin resonance,hole spin,quantum dot,GaAs,spin-orbit interaction
更新于2025-09-12 10:27:22
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Impact of Proton and Electron Irradiation-Induced Defects on the Dark Current of GaAs Solar Cells
摘要： The same amount of non-ionizing energy is deposited in GaAs solar cells through 1 MeV proton and electron radiation at specific fluence values. The defects created are detected and characterized via temperature-dependent dark I–V analysis, and the energy levels are correlated to trap states observed via admittance spectroscopy. A remarkable difference is observed between the defect energy levels introduced in the proton and electron cases: in the former, the recombination centers lie around the mid-gap position, while in the latter they are spread over a wider energy range in the band-gap. This induces a profound difference in the degradation of the recombination current in the space-charge region. On the other hand, the degradation of the diffusion current in the neutral regions is found to be determined by the recombination velocities at the back and front hetero-interfaces of the solar cell. They depend only on the displacement damage dose and are independent of the particle type.
关键词： recombination current,semiconductor device modeling,surface recombination,Displacement damage,irradiation-induced defect,GaAs solar cell
更新于2025-09-12 10:27:22
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Performance Improvement of Trough Concentrating Photovoltaic Thermal System: A Review
摘要： This paper presents an overview on the performance improvement of trough concentrating photovoltaic thermal system by optimizing different components and operating parameters of the system and has been put forwarded. Initially, the performance of four types of solar cell arrays was studied, in that triple junction GaAs cells possessed good performance characteristics. Subsequently the importance of increasing the concentrator reflectivity for improving the performance of TCPV/T system is presented by increasing the mirror reflectivity from 0.69 to 0.92 and consequently the maximum power of the cell array got increased. Then, the role of receiver shape like rectangle and triangle for the maximum utilization of solar radiation is also presented.
关键词： Concentrator reflectivity,GaAs,PV cells,trough collector,Heat transfer
更新于2025-09-12 10:27:22
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Improved spectral and temporal response of MSM photodetectors fabricated on MOCVD grown spontaneous AlGaAs superlattice
摘要： A co-planar metal-semiconductor-metal nonsymmetrical back to back Schottky diode photodetector using natural superlattice AlGaAs grown by metalorganic vapor phase epitaxy on GaAs (100) has been reported. The detection efficiency and photoresponse of the superlattice based device are found significantly superior compared to the one based on high temperature annealed homogeneous AlGaAs. Under a forward bias of 1 V, the peak values of responsivity, detectivity and sensitivity were 10.133 mA/W, 7.6 × 1011 cmHz1/2W?1, 81.06 cm2/W for the device with as-grown natural superlattice and 1.14 mA/W, 7.05 × 1010 cmHz1/2W?1, 2.82 cm2/W for the device with homogeneous composition of AlGaAs, respectively. Besides, the device with natural superlattice structure showed much faster response to the pulsed light with rise and decay time of 560 μs and 1 ms as compared to 2 and 7 ms, respectively for the device with disordered bulk AlGaAs. The superior spectral and temporal characteristics of the device are explained by a model based on a third diode representing the net effect due to the superlattice modulations along with two Schottky diodes at the metal-semiconductor junctions. The third barrier, which is basically due to the periodic modulation in aluminium composition, plays an important role in enhancement of the photocurrent owing to the activation of the superlattice channels under light while keeping the dark current small. The fast sweeping of the photogenerated carries by the intrinsic electric field at the heterointerfaces in the active semiconducting layer makes the characteristic times of the device with the superlattice structures much smaller than one with homogeneous AlGaAs. Degradation in photoresponse and speed is attributed to the interdiffusion as an effect of thermal annealing.
关键词： AlGaAs/GaAs,Spectral response,Metal-semiconductor-metal photodetector,Natural superlattice,Temporal response
更新于2025-09-12 10:27:22
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Thermal-stress distribution and damage characteristics of three-junction GaAs solar cell irradiated by continuous laser beam
摘要： According to the theory of Fourier heat transfer and thermal stress field, a model on thermal damage of three-junction GaAs solar cell is established. The temperature and thermal-stress distribution inside the solar cell, which irradiated by continuous laser, are calculated. Results show that the temperature and thermal-stress distribution are corresponded to the intensity distribution of the incident laser beam. The maximum values of the compressive and tensile stress increase with the increasing of the power density and waist radius of the incident laser. When the waist radius is 0.5 cm, the melting damage is the main damage pattern as the power density is below about 40 W/cm2. However, when the laser power density is higher the stress damage will change to the main damage form. As the waist radius increases, the change in damage processes will also occur at lower laser power density.
关键词： Three-junction GaAs solar cell,Thermal-stress,Continuous laser beam,Damage
更新于2025-09-12 10:27:22