A5004083927- GaN-based semiconductor devices and materials
- Semiconductor materials and devices
- Semiconductor Quantum Structures and Devices
- Graphene research and applications
- Ga2O3 and related materials
- Metal and Thin Film Mechanics
- Membrane Separation Technologies
- Silicon Carbide Semiconductor Technologies
- Radio Frequency Integrated Circuit Design
- Advanced Semiconductor Detectors and Materials
- Photonic and Optical Devices
- Nanopore and Nanochannel Transport Studies
- Fuel Cells and Related Materials
- ZnO doping and properties
- Membrane-based Ion Separation Techniques
- Fault Detection and Control Systems
- Control Systems and Identification
- Spacecraft and Cryogenic Technologies
- Advanced Control Systems Optimization
- Advanced Optical Sensing Technologies
- Electric and Hybrid Vehicle Technologies
- Energy, Environment, and Transportation Policies
- Photocathodes and Microchannel Plates
- Fiber-reinforced polymer composites
- Molecular Junctions and Nanostructures
Pacific Northwest National Laboratory
2013-2024
Battelle
2019
Stockholm University
2012
Veeco (United States)
2005-2008
The University of Texas at Austin
1997-2004
Emcore (United States)
2001-2004
Luleå University of Technology
1996-1997
Abstract Membranes made of stacked layers graphene oxide (GO) hold the tantalizing promise revolutionizing desalination and water filtration if selective transport molecules can be controlled. We present findings an integrated study that combines experiment molecular dynamics simulation intercalated between GO layers. simulated a range hydration levels from 1 wt.% to 23.3 water. The interlayer spacing increased upon 0.8 nm 1.1 nm. also synthesized membranes showed increase in layer about 0.7...
We demonstrated that Sc2O3 thin films deposited by plasma-assisted molecular-beam epitaxy can be used simultaneously as a gate oxide and surface passivation layer on AlGaN/GaN high electron mobility transistors (HEMTs). The maximum drain source current, IDS, reaches value of over 0.8 A/mm is ∼40% higher Sc2O3/AlGaN/GaN relative to conventional HEMTs fabricated the same wafer. metal–oxide–semiconductor (MOS–HEMTs) threshold voltage in good agreement with theoretical value, indicating retains...
A study of V/Al/Pt/Au and Ti/Al/Pt/Au contacts to n-Al0.3Ga0.7N/GaN heterostructures is presented. Vanadium was chosen as a potential replacement for Ti because V expected form thermally stable nitride with low work function. Low-resistance Ohmic are achieved layers after annealing at 650 °C, which represents decrease 150 °C compared the counterpart. This contact exhibits two orders magnitude lower specific resistance studied in this when annealed temperatures less than 800 although higher...
Abstract A polyethersulfone (PES)-supported graphene oxide (GO) membrane has been developed by a simple casting approach. This stable is applied for ethanol/water separation at different temperatures. The 5.0 µm thick GO film coated on PES support showed long-term stability over testing period of one month and excellent water/ethanol selectivity elevated dependent ethanol weight percentage in feed mixtures operating temperature. was enhanced with an increase mixtures, from below 100 RT to...
Intra- and interlayer atom-atom correlations in molecular beam epitaxially grown dilute InGaAs alloys were studied using cross-sectional scanning tunneling microscopy. By imaging individual chemical constituents we construct a large ensemble of ``atom maps'' from which two-dimensional In-In pair correlation functions deduced. We found total absence along $[001]$ strong negative for the nearest neighbor (nn) $[110]$, corresponding to repulsive interaction energy 0.1 eV nn In pairs $[110]$....
A comparison was made of specific contact resistivity and morphology Ti/Al/Pt/WSi/Ti/Au Ti/Al/Pt/W/Ti/Au ohmic contacts to AlGaN/GaN heterostructures relative the standard Ti/Al/Pt/Au metallization. The W- WSi-based show comparable resistivities that on similar layer structures, reaching minimum values ∼10−5 Ω cm2 after annealing in range 850–900 °C. However, exhibit much smoother surface morphologies, even 950 °C annealing. For example, root-mean-square roughness annealed at unchanged from...
Hierarchically stacked graphene oxide (GO) membranes have been observed to undergo physical and chemical changes under ambient conditions. In this study, the slow degradation of GO is mimicked accelerated by UV light (254 nm) exposure. Spectroscopic X-ray diffraction analyses confirm that changes, including macroscopic as well atomic-scale alterations, cannot be attributed loss intercalated water molecules between sheets, but exposure triggers a partial reduction membrane more graphene-like material.
A high efficiency nitrogen rf plasma source has been used to grow GaNAs by diluting the N2 gas with Ar. This (an EPI UniBulb™ source) was originally designed for use in growth of pure nitrides at rates. For As-rich GaNAs, concentrations active lead GaN instead a random alloy. In this work we demonstrate that dilute N2/Ar mixture leads films where amount incorporation varies directly percentage mixture. Films structural quality were grown, thus validating approach.
A resonant-cavity avalanche photodiode using a GaNAs absorption region grown on GaAs has been demonstrated. The peak quantum efficiency was 59% at 1.064 μm with full width half maximum of 11 nm. coefficient determined to be α=9×103/cm this wavelength. devices exhibited gain up 100 low breakdown voltage 13 V.
High-performance, low-noise AlGaN/GaN high electron mobility transistors (HEMTs) with 0.25 µm gate-length have been fabricated on semi-insulating 6H‐SiC substrates. The devices exhibited a unity current gain cutoff frequency (fT) of 52.3 GHz, and maximum oscillation (fMAX) 112 GHz. At 10 minimum noise figure (NFmin) 0.75 dB an associated (Ga) 10.84 was obtained when biased at VDS=10 V IDS=40.6 mA/mm. corresponding values were 1.15 7.49 18 These results are the first reported microwave...
In this article we report record power densities in GaN HEMTs operating at 40 GHz. Devices fabricated with 0.18 /spl mu/m long e-beam gates showed a density of 2.82 W/mm and gain 5.8 dB This performance was obtained due to combination high gain, negligible RF dispersion, breakdown voltage.
Using cross-sectional scanning tunneling microscopy, we have investigated factors which influence interfacial roughness in InGaAs/GaAs heterostructures and found that the of growth front In segregation are two major influencing roughness. addition, noticed no preferential clustering indium atoms along [001] direction as previously reported by others. Furthermore, a procedure combines substrate temperature ramping with interruption results an atomically smooth interface.
Passivated AlGaN-GaN high electron mobility transistor (HEMT) structures are modified by adding a MOS test gate placed between and drain to identify surface charge phenomena stress experiments. A new method is described the vertical position of centroid injected from gate. In case investigated, this within passivation layer.
In this work, the authors report step-flow growth mode of InN on [0001] oriented GaN templates, using a production-style molecular beam epitaxy system, Veeco GEN200®, equipped with plasma source. Using adaptive conditions, they have obtained surface morphology that exhibits features. The root mean squared roughness over an area 5×5μm2 is 1.4nm monolayer height terrace steps (0.281nm), based atomic force microscopy. It has been found presence droplets leads to defective morphology. From x-ray...
We report on the epitaxial growth and characterization of gallium nitride by molecular beam epitaxy (MBE). The samples were grown (0002) sapphire using solid metal group III sources an EPI UniBulb™ rf plasma source to produce atomic neutral nitrogen species. films characterized optically reflectance photoluminescence, van der Pauw Hall effect measurements, x-ray rocking curves for (0002), (101̄4), (22̄04) directions. Nominally undoped with a curve (ω) full width at half maximum (FWHM) from...
A p-i-n avalanche photodiode (APD) using GaNAs grown on GaAs has been demonstrated. Characterization of the excess noise in material was used to determine that ratio ionization coefficients (k=β/α) is k=0.4. The quantum efficiency above 25% at 0.94 μm for 0.75% nitrogen incorporation. APDs exhibited low dark currents (<60 nA/mm2 90% breakdown) and a gain-bandwidth product 42 GHz. therefore shows promise extending operation GaAs-based longer wavelengths.