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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Ultrahigh sensitive sub-terahertz detection by InP-based asymmetric dual-grating-gate high-electron-mobility transistors and their broadband characteristics

We report on room-temperature plasmonic detection of sub-terahertz radiation by InAlAs/InGaAs/InP high electron mobility transistors with an asymmetric dual-grating-gate structure. Maximum responsivities of 22.7 kV/W at 200 GHz and 21.5 kV/W at 292 GHz were achieved under unbiased drain-to-source condition. The minimum noise equivalent power was estimated to be 0.48 pW/Hz{sup 0.5} at 200 GHz at room temperature, which is the record-breaking value ever reported for plasmonic THz detectors. Frequency dependence of the responsivity in the frequency range of 0.2–2 THz is in good agreement with the theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Characteristics of InGaAsBi with various lattice mismatches on InP substrate

To develop bismuth-containing infrared optoelectronic devices, InGaAsBi/InP films with different lattice mismatches have been investigated. The lattice mismatch was tailored by changing the Bi content in conjunction with the In content simultaneously. X-ray diffraction analysis revealed that alloy lattice constants have been extended positively by incorporation of Bi into the crystal lattice. Electrical and optical characteristics were investigated by Hall-effect, optical absorption and photoluminescence measurements. A bandgap shrinking of about 56.4 meV/Bi% was deduced by X-ray diffraction and optical absorption measurements. From the excitation dependent photoluminescence measurement at 10 K, the donor-acceptor pair emissions were inferred for samples containing moderate and high levels of Bi. The temperature dependence of the PL peak energy is as small as 0.06 meV/K in In{sub 0.5}Ga{sub 0.5}As{sub 0.987}Bi{sub 0.013}, which is fairly low compared with that of In{sub 0.5}Ga{sub 0.5}As.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of growth interruption in 1.55 μ m InAs/InAlGaAs quantum dots on InP grown by molecular beam epitaxy

We report the effect of growth interruptions on the structural and optical properties of InAs/InAlGaAs/InP quantum dots using molecular beam epitaxy. We find that the surface quantum dots experience an unintended ripening process during the sample cooling stage, which reshapes the uncapped InAs nanostructures. To prevent this, we performed a partial capping experiment to effectively inhibit structural reconfiguration of surface InAs nanostructures during the cooling stage, revealing that InAs nanostructures first form quantum dashes and then transform into quantum dots via a ripening process. Our result suggests that the appearance of buried InAs/InAlGaAs nanostructures can be easily misunderstood by surface analysis.

Jung, Daehwan↗
DOE OSTI2019

Influence of the polarization anisotropy on the linewidth enhancement factor and reflection sensitivity of 1.55- μ m InP-based InAs quantum dash lasers

This work investigates the effect of the polarization anisotropy on the linewidth enhancement factor and the reflection sensitivity of InAs/InP quantum dash semiconductor lasers. The results show that the small linewidth enhancement factor and high stability against external optical feedback are obtained for nanostructures oriented perpendicular to the cavity axis as opposed to those oriented parallel to the cavity axis. Effective simulations on the critical feedback level of these two lasers are also in agreement with experimental results. Such anisotropy is attributed to the polarization dependence of the transition matrix element in these quantum nanostructures.

Dong, B. (ORCID:0000000158266723)↗
DOE OSTI2020

Comparison of amplification via the acousto-electric effect of Rayleigh and Leaky-SAW modes in a monolithic surface InP:InGaAs/lithium niobate heterostructure

This work demonstrates a monolithic surface acoustic wave amplifier fabricated by state-of-the-art heterogenous integration of a III-V InGaAs-based epitaxial material stack and LiNbO 3 . We compare amplification of Raleigh-SAW and leaky-SAW modes on a on Y-cut, X-propagating delay line amplifier. Due to the superior properties of the materials employed, we observe a net terminal gain of 3dB for an LSAW overtone mode This platform enables further advances in active and non-reciprocal piezoelectric acoustic devices.

42 ENGINEERING↗
DOE OSTI2015

Photoluminescence Imaging Characterization of Thin-Film InP

Indium phosphide grown using a novel vapor-liquid-solid method is a promising low-cost material for III-V single-junction photovoltaics. In this work, we characterize the properties of these materials using photoluminescence (PL) imaging, time-resolved photoluminescence (TRPL), and microwave-reflection photoconductive decay (u-PCD). PL image data clearly shows the emergence of a self-similar dendritic growth network from nucleation sites, while zoomed-in images show grain structure and grain boundaries. Single photon TRPL data shows initial surface-dominated recombination, while two-photon excitation TRPL shows a lifetime of 10 ns. Bulk carrier lifetime may be as long as 35 ns as measured by u-PCD, which can be less sensitive to surface recombination.

14 SOLAR ENERGY↗
DOE OSTI2014

Radoptic Effect in InP and GaN for Ultrafast Scintillator Applications

Ultrafast scintillators are the subject of current research in an effort to better resolve ultrafast phenomena in high-energy density physics (HEDP) experiments. Despite extensive research on new scintillator materials, the essential mechanism of energy absorption, excitation, and photo-emission has remained unchanged for over 50 years. Recently, a new class of semiconductor detector has been developed utilizing the radoptic effect, or the change of refractive index when subjected to radiation, in an attempt to record events faster than conventional scintillators.1 This study was designed for the observation of the radoptic effect by optical interferometry in different semiconductors to experimentally determine the fastest and most sensitive materials for the optimization of current radsensors.

radoptic, scintillator, ultrafast, semiconductor↗
DOE OSTI2015

Site-Controlled Growth of Single InP QDs

The MOVPE growth of InP/GaInP quantum dots (QDs) on GaAs substrate “defects” formed by a focused beam of Ga{sup +} ions is studied. It is shown that ordered arrays of QDs with a density of 0.25 (μm){sup −2} can be obtained in the InP/GaInP system. It is demonstrated that effective luminescence can be obtained by using two QD sheets separated by a GaAs/GaInP buffer layer.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Electron properties of surface InGaAs/InAlAs quantum wells with inverted doping on InP substrates

The electron-transport and optical properties of heterostructures with a surface InGaAs/InAlAs quantum well in the cases of inverted δ doping with Si atoms (below the quantum well) and of standard δ doping (above the quantum well) are compared. It is shown that, in the case of inverted doping, the two-dimensional electron density in the quantum well is increased in comparison with the case of the standard arrangement of the doping layer at identical compositions and thicknesses of other heterostructure layers. The experimentally observed features of low-temperature electron transport (Shubnikov–de Haas oscillations, Hall effect) and the photoluminescence spectra of heterostructures are interpreted by simulating the band structure.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Second-Harmonic Generation of Subterahertz Gyrotron Radiation by Frequency Doubling in InP:Fe and Its Application for Magnetospectroscopy of Semiconductor Structures

The possibility of obtaining intense terahertz radiation due to second-order lattice nonlinearity in indium-phosphide crystals doped with iron is discussed. As a source of radiation, subterahertz gyrotrons are considered. It is shown that the efficiency of frequency doubling can reach 3%, which opens up the possibility for developing a new generation of terahertz radiation sources. The possibility of applying second-harmonic radiation for the magnetospectroscopy of semiconductor structures with quasi-Dirac dispersion is demonstrated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Luminescence Properties of GaInAsP Layers with Graded Composition–Depth Profiles Grown on InP Substrates

Luminescence properties of epilayers of Ga{sub 1 –x}In{sub x}As{sub y}P{sub 1 –y} (GaInAsP) solid solutions with graded content of Group V elements (Δy up to 0.08 over a total thickness of about 1 μm) were studied at 77 and 300 K. The photoluminescence (PL) spectra of GaInAsP epilayers with large Δy values were broadened. The GaInAsP epilayers of low crystalline perfection exhibited either no PL emission or showed PL spectra characteristic of transitions involving impurity energy levels.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗