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High-frequency breakdown of the integer quantum Hall effect in GaAs/AlGaAs heterojunctions
摘要： The integer quantum Hall effect is a well-studied phenomenon at frequencies below about 100 Hz. The plateaus in high-frequency Hall conductivity were experimentally proven to retain up to 33 GHz, but the behavior at higher frequencies has remained largely unexplored. Using continuous-wave terahertz spectroscopy, the complex Hall conductivity of GaAs/AlGaAs heterojunctions was studied in the range of 69–1100 GHz. Above 100 GHz, the quantum plateaus are strongly smeared out and replaced by weak quantum oscillations in the real part of the conductivity. The amplitude of the oscillations decreases with increasing frequency. Near 1 THz, the Hall conductivity does not reveal any features related to the filling of Landau levels. Similar oscillations are observed in the imaginary part as well; this effect has no analogy at zero frequency. This experimental picture is in disagreement with existing theoretical considerations of the high-frequency quantum Hall effect.
关键词： integer quantum Hall effect,GaAs/AlGaAs heterojunctions,terahertz spectroscopy,high-frequency Hall conductivity,quantum oscillations
更新于2025-09-23 15:22:29
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A detailed comparison of measured and simulated optical properties of a short-period GaAs/Al <sub/><i>x</i> </sub> Ga <sub/> 1a?? <i>x</i> </sub> As distributed Bragg reflector
摘要： A 6-period GaAs/Al0.9Ga0.1As distributed Bragg re?ector (DBR) has been grown and its optical properties have been both measured and simulated. Incremental improvements were made to the simulation, allowing it to account for internal consistency error, incorrect layer thicknesses, and absorption due to substrate doping to improve simulation accuracy. A compositional depth pro?le using secondary-ion mass spectrometry (SIMS) has been taken and shows that the Al fraction averages 88.0% ± 0.3%. It is found that the amplitude of the transmission is signi?cantly affected by absorption in the n-doped GaAs substrate, even though the energy of the transmitted light is well below the GaAs band gap. The wavelength of the features in the transmission spectrum are mostly affected by DBR layer thicknesses. On the other hand, the transmission spectrum is found to be relatively tolerant to changes to Al fraction.
关键词： optical simulation,AlGaAs,distributed Bragg re?ector,SIMS,cross section,telecoms,vertical cavity
更新于2025-09-23 15:21:01
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Light-induced transition between the strong and weak coupling regimes in planar waveguide with GaAs/AlGaAs quantum well
摘要： Exciton-polaritons in planar waveguides are of great interest for application in polariton circuits due to the large polariton group velocity in the plane of the waveguide. We demonstrate the ability to control the exciton-polariton coupling by light in an AlGaAs-based planar waveguide with GaAs/AlGaAs quantum well. The transition between strong and weak coupling regimes observed with increasing light intensity is explained by the increase in exciton mode losses due to the quantum well charging. This assumption is confirmed by the reflection spectroscopy with resonant illumination.
关键词： AlGaAs,GaAs,planar waveguides,strong coupling,quantum well,exciton-polaritons,weak coupling
更新于2025-09-23 15:21:01
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Higha??temperature droplet epitaxy of symmetric GaAs/AlGaAs quantum dots
摘要： We introduce a high–temperature droplet epitaxy procedure, based on the control of the arsenization dynamics of nanoscale droplets of liquid Ga on GaAs(111)A surfaces. The use of high temperatures for the self-assembly of droplet epitaxy quantum dots solves major issues related to material defects, introduced during the droplet epitaxy fabrication process, which limited its use for single and entangled photon sources for quantum photonics applications. We identify the region in the parameter space which allows quantum dots to self–assemble with the desired emission wavelength and highly symmetric shape while maintaining a high optical quality. The role of the growth parameters during the droplet arsenization is discussed and modeled.
关键词： GaAs/AlGaAs,quantum photonics,arsenization dynamics,high–temperature droplet epitaxy,quantum dots
更新于2025-09-23 15:21:01
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Steering second-harmonics
摘要： The phase control and shaping of the second-harmonic radiation generated from an AlGaAs nanodisk antenna has now been accomplished by a team of researchers from Italy, France and Australia. Lavinia Ghirardini and co-workers used electron-beam lithography to fabricate a pair of gratings located either side of a nonlinear nanoantenna. Phase engineering then made it possible to redirect and control the emission angle of second-harmonic light generated from the optically pumped structure. The precise angle of emission can be engineered by employing gratings with different symmetry, or by varying the polarization of the optical pump beam. The control of the emission direction is important because it means that two orders of magnitude more power can be collected out of the antenna plane and arbitrary emission angles could be useful for certain applications. Another key point is that the AlGaAs structures can exhibit lower losses than metallic nanoantennas, which aid efficiency. Such efficient shaping of the nonlinear beams may have applications to, for example, single-photon sources and nonlinear imaging.
关键词： phase control,AlGaAs,nanoantenna,second-harmonics,nonlinear imaging
更新于2025-09-23 15:21:01
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Elastic Properties of Suspended Conducting GaAs/AlGaAs Nanostructures by Means of Atomic Force Microscopy
摘要： This paper demonstrates the applicability of nanoindentation technique using atomic-force microscope cantilever for studying the elastic properties of suspended semiconductor structures on the basis of relatively thick GaAs/AlGaAs membranes in the case when their stiffness significantly exceeds that of the cantilever of atomic-force microscope, which is confirmed by the agreement between the experimentally determined values of both relative and absolute stiffness measured at different points of the investigated structure with theoretical predictions.
关键词： nanoelectromechanical systems,GaAs/AlGaAs,atomic-force microscopy,suspended nanostructures
更新于2025-09-19 17:15:36
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1.73 eV AlGaAs/InGaP heterojunction solar cell grown by MBE with 18.7% efficiency
摘要： We report on AlGaAs-based heterojunction solar cells grown by solid source molecular beam epitaxy (MBE). We investigate InGaP and AlGaAs material quality and we demonstrate significant efficiency improvements by combining the best of each alloy: a thick p-AlGaAs base with tunable bandgap, and a thin 50 nm n-InGaP emitter separated by a thin intrinsic AlGaAs layer. We report a certified solar cell conversion efficiency of 18.7% with a 2-μm-thick AlGaAs layer and a bandgap of 1.73 eV, suitable for high efficiency Si-based tandem devices.
关键词： AlGaAs,MBE,InGaP,III-V solar cells,heterostructure
更新于2025-09-19 17:13:59
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All-Dielectric Nanoresonators for ??(2) Nonlinear Optics
摘要： Metal-less nanophotonics offers new opportunities for non-linear optics with respect to optical waveguides and microresonators, taking advantage of the progress within nanofabrication to boost the development of subwavelength Mie-type structures. Here, we review recent results on second harmonic generation with semiconductor nanoresonators, focusing on their scattering features in terms of efficiency and control over radiation patterns. First, two theoretical models are comparatively discussed with a view to possible improvements in analysis and design. Then, some relevant experiments are reported, and the origin of the χ(2) generation is discussed, outlining the main open topics to investigate in the near future and the advantages offered by these nanostructures to the development of novel photonic devices.
关键词： Mie resonances,second harmonic generation,AlGaAs nanoresonators,all-dielectric resonators,nanophotonics
更新于2025-09-19 17:13:59
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Time-resolved measurements of two-color laser light emitted from GaAs/AlGaAs-coupled multilayer cavity
摘要： We measured the two-color laser oscillation from a GaAs/AlGaAs-coupled multilayer cavity at 18 °C–42 °C using current injection. We confirmed simultaneous lasing by detecting the sum frequency generation signal generated by the two-color laser light, and performed time-resolved measurement using a streak camera with a spectrometer. From the observed time transient of the spectra at various temperatures, it is clarified that the temperature change of the device, induced by current injection, modulates the effective cavity length. Therefore, the temperature control of the device is a key factor in stable two-color lasing and THz wave generation.
关键词： time-resolved measurements,sum frequency generation,THz wave generation,GaAs/AlGaAs-coupled multilayer cavity,two-color laser
更新于2025-09-19 17:13:59
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Effects of P-N Junction Built-In Electric Field on Ir-Led Resistance under Gamma Rays Irradiation
摘要： It is known that the rate of introduction of radiation defects into the Schottky barrier of GaAs and InP diodes depends on the presence of the electric field. The main aim of this research is to study the influence of the built-in electric field at the p-n junction on the resistance of dual AlGaAs heterostructure IR-LEDs under gamma rays irradiation. It is determined that the rate of defects introduction in the presence of built-in electric field or reverse bias at p-n junction is considerably less than the rate of defects introduction into the neutral region without electric field. Then the possible ways of improving the radiation resistance of infrared LEDs are considered.
关键词： heterostructures,p-n junction,AlGaAs,light emitting diodes,gamma ray
更新于2025-09-16 10:30:52