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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) - f <sub/>max</sub> =800 GHz with 75 nm gate length and asymmetric gate recess for InGaAs/InAlAs PHEMT
摘要： In This paper, we present a high maximum frequency of oscillation (fmax) and a current-gain cutoff frequency (fT) of 800 GHz and 260 GHz respectively with pseudomorphic high-electron mobility transistor (PHEMT), using a composite, InGaAs/InAs/InGaAs channel and an asymmetric gate recess. This result was achieved with long gate length LG = 75 nm. The noise performance has been explored until 110 GHz, and gives a minimum noise figure NFmin = 0.8 dB (1.8 dB) with associated gain Gass = 16 dB (11.6 dB) at 40 GHz (94 GHz). Moreover extending the drain recess length to 225 nm and reducing the gate to source distance by 200 nm allows a fmax = 1.2 THz.
关键词： noise performance,InGaAs/InAs/InGaAs channel,asymmetric gate recess,PHEMT,high frequency
更新于2025-09-16 10:30:52
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Non-radiative recombination at dislocations in InAs quantum dots grown on silicon
摘要： We study the impact of misfit dislocations on the luminescence from InAs quantum dots (QDs) grown on Si substrates. Electron channeling contrast imaging is used together with cathodoluminescence mapping to locate misfit dislocations and characterize the resulting nonradiative recombination of carriers via near-infrared light emission profiles. With a 5 kV electron beam probe, the dark line defect width due to a typical misfit dislocation in a shallow QD active layer is found to be approximately 1 lm, with a 40%–50% peak emission intensity loss at room temperature. Importantly, we find that at cryogenic temperatures, the dislocations affect the QD ground state and the first excited state emission significantly less than the second excited state emission. At the same time, the dark line defect width, which partially relates to carrier diffusion in the system, is relatively constant across the temperature range of 10 K–300 K. Our results suggest that carrier dynamics in the QD wetting layer control emission intensity loss at dislocations, and that these defects reduce luminescence only at those temperatures where the probability of carriers thermalizing from the dots into the wetting layer becomes significant. We discuss the implications of these findings toward growing dislocation-tolerant, reliable quantum dot lasers on silicon.
关键词： silicon substrates,nonradiative recombination,quantum dot lasers,InAs quantum dots,cathodoluminescence,misfit dislocations
更新于2025-09-16 10:30:52
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[IEEE 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - Bhopal, India (2019.12.19-2019.12.21)] 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - Stub Loaded Semi-Circular Resonator for Filter Applications
摘要： Tunnel FETs (TFETs) have been identified as the most promising steep slope devices for ultralow power logic circuits. In this paper, we demonstrate in-plane InAs/Si TFETs monolithically integrated on Si, using our recently developed template-assisted selective epitaxy approach. These devices represent some of the most scaled TFETs with dimensions of less than 30 nm, combined with excellent aggregate performance with average subthreshold swing (SS), of around 70 mV/decade combined with ION of a few μA/μm for |VDS| = |VGS| = 0.5 V. Here, we will discuss the device fabrication as well as the experimental electrical data. Extensive low temperature characterization and activation energy analysis is used to gain insights into the factors limiting device performance. Combined with the simulation study presented in part 2 of this paper, this will elucidate how traps are ultimately limiting the SS.
关键词： selective epitaxy,tunnel FET (TFET),InAs,Heterojunction device
更新于2025-09-16 10:30:52
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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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Broad tunability of emission wavelength by strain coupled InAs/GaAs <sub/>1???x</sub> Sb <sub/>x</sub> quantum dot heterostructures
摘要： Tuning of the photoluminescence emission over a wider range of optical telecommunication wavelength (1.38 μm–1.68 μm) has been achieved by employing a GaAs1 ? xSbx capping layer to the strain coupled bilayer InAs quantum dot (QD) heterostructures. It is shown that the modulation of strain between the two dot layers through variation in Sb-content and thickness of the capping layer strongly influence the dot size. The band alignment transformation from type-I to type-II is observed for high Sb-content in the capping layers. In addition, the carrier lifetime is improved by a factor of three in the QD heterostructures having type-II band alignment. This, we believe, is of importance for optoelectronic device applications.
关键词： GaAs1 ? xSbx capping layer,carrier lifetime,optoelectronic device applications,photoluminescence emission,strain coupled bilayer InAs quantum dot,type-I to type-II band alignment,optical telecommunication wavelength
更新于2025-09-12 10:27:22
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High-detectivity infrared photodetector based on InAs submonolayer quantum dots grown on GaAs(001) with a 2?×?4 surface reconstruction
摘要： The submonolayer quantum dots of an infrared photodetector were grown by molecular beam epitaxy in the presence of a very low As ?ux and a 2 × 4 surface reconstruction in order to e?ectively nucleate small two-dimensional InAs islands that are required to form such nano-structures. A speci?c detectivity of 9.2 × 1010 cm Hz1/2 W?1 was obtained at 10 K with a bias of 1.0 V.
关键词： InAs submonolayer quantum dots,2 × 4 surface reconstruction,molecular beam epitaxy,infrared photodetector,GaAs(001)
更新于2025-09-12 10:27:22
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Growth Habits of Bismuth Selenide (Bi2Se3) layers and nanowires over Stranski–Krastanov Indium Arsenide Quantum Dots
摘要： Bismuth selenide layers and nanowires have been grown by molecular beam epitaxy on self-assembled Stranski–Krastanov InAs quantum dots of different sizes and densities on GaAs substrates. The size and density of the InAs quantum dots were modified by changes in the growth rate and composition. The structure and growth habits of the Bi2Se3 layers were studied by high-resolution x-ray diffraction, scanning probe microscopy, energy-dispersive x-ray spectroscopy and high-resolution electron microscopy. The epitaxial growth of continuous layers of (0001) Bi2Se3 was observed over flat InAs surfaces. In contrast, the presence of InAs quantum dots induced the growth of 100 nm-long and 20 nm-wide Bi2Se3 nanowires primarily oriented along [01-1] and [0-1-1] directions. The nanowires coalesced into full layers when the growth proceeded further. Better understanding and control of the Bi2Se3 growth habits over these surfaces should lead to novel nanostructures with enhanced physical properties.
关键词： InAs quantum dots,Bi2Se3,nanowires,topological insulator,Bismuth selenide,molecular beam epitaxy
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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Novel approach to passivation of InAs/GaSb type II superlattice photodetectors
摘要： The innovative two-step passivation by octadecanethiol (ODT) self-assembled monolayers (SAMs) and the following silicon dioxide (SiO2) deposition was used for the type-II InAs/GaSb superlattice photodetector. To understand the mechanism of passivation, the (100) GaSb surface covered with the ODT and, for comparison, with the biphenyl thiol (BPT), was characterized by the atomic force microscopy, Raman spectroscopy and contact angle analysis. The results of the study indicated the presence of the homogeneous both the ODT and the BPT monolayers; however, the ODT SAMs were more stable. Therefore, the ODT-based wet treatment was used in the two-step passivation resulting in a reduction of the dark current by one order of magnitude for passivated detector compared with an unpassivated device.
关键词： ODT,SiO2,InAs/GaSb superlattice,BPT,photodetectors,passivation
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019 - Erode, India (21–22 November 2019)] SECOND INTERNATIONAL CONFERENCE ON MATERIAL SCIENCE, SMART STRUCTURES AND APPLICATIONS: ICMSS-2019 - Modeling of optical characteristics of near-infrared photodetectors on the basis of InAs/GaAs heterointerfaces
摘要： A mathematical model for simulation of optical and functional characteristics of InAs/GaAs heterointerfaces with one layer of InAs quantum dots has been developed. The presence of the peak of the main optical transitions in quantum dots of 1.2 eV (modeling) and 1.12 eV (experimental) is demonstrated. The experimental photoluminescence peak has a greater width (0.13 eV) at half the maximum radiation of the main transitions in quantum dots compared to the simulated one (0.06 eV). A red shift of the experimental peak by approximately 65 meV is observed, which indicates the presence of a size variance of quantum dots in the real heterointerface. The modeled distribution of the dark current-voltage characteristic at 90 K and zero shift reveals the value of the dark current density of 10-7 A/cm2, which is an order of magnitude less than the measurement results (10-6 A/cm2). The difference in the pattern of dependence distribution at negative and positive bias associated with the presence of quantum dots of larger size is observed.
关键词： quantum dots,InAs/GaAs heterointerfaces,photoluminescence,dark current-voltage characteristics
更新于2025-09-12 10:27:22