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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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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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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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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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Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations
摘要： Radio-frequency modulated terahertz (THz) emission power from weakly-coupled GaAs/AlGaAs superlattice (SL) has been increased by parallel connection of several SL mesas. Each SL mesa is a self-oscillator with its own oscillation frequency and mode. In coupled non-identical SL mesas biased at different voltages within the hysteresis loop the chaotic, quasiperiodic and frequency-locked modes of self-oscillations of current arise. THz emission was detected when three connected in parallel SL mesas were biased into the frequency-locked and quasiperiodic modes of self-oscillations of current, while in the chaotic mode of those it falls to the noise level.
关键词： current self-oscillations,quasiperiodic mode,terahertz emission,frequency-locked mode,GaAs/AlGaAs superlattice,chaotic mode
更新于2025-09-11 14:15:04
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Effects of barrier energy offset and gradient in extended wavelength infrared detectors
摘要： The extended wavelength infrared photodetectors are new class of III-V semiconductor heterojunction-based photodetectors that can detect incoming radiation with an energy significantly smaller than the minimum energy gap (Δ) at the heterojunction interface. Architecture of these photodetectors include a barrier-emitter-barrier epilayers sandwiched between highly doped ohmic top and bottom contact layers. An energy offset (????) between the barriers is necessary for the extended wavelength photodetection. In this work, we study the performance of extended wavelength infrared photodetectors with varying ???? and gradient of the potential barrier. Results indicate that the extended wavelength threshold varied slightly with varying both the gradient and offset. Spectral responsivity, however, increased with the increasing offset and decreased with increasing gradient.
关键词： Extended wavelength infrared photodetectors,III-V semiconductors,GaAs/AlGaAs heterostructures
更新于2025-09-09 09:28:46
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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