Eden Prairie, MN, United States

Agnitron Technology Inc.

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Eden Prairie, MN, United States

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Polyakov A.Y.,Institute of Rare Metals | Smirnov N.B.,Institute of Rare Metals | Kozhukhova E.A.,Institute of Rare Metals | Osinsky A.V.,Agnitron Technology Inc. | Pearton S.J.,University of Florida
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures | Year: 2013

Nominally undoped GaN films were grown by metalorganic chemical vapor deposition under three different conditions, namely (1) "standard" growth conditions with growth temperature of 1000 °C and growth rate of 1 μm/h, (2) slightly reduced growth temperature of 975 °C, and (3) standard temperature, but higher growth rate of 2.5 μm/h. The standard sample had a net donor density <1015 cm-3, while the two other samples were semi-insulating, with sheet resistivity ∼1014 Ω/square and the Fermi level pinned at Ec-0.8 eV for the low temperature growth and at Ec-0.9 eV for the high growth rate conditions. The photoconductivity spectra of both of these latter samples show the presence of centers with optical threshold near 1.35 eV commonly attributed to C interstitials and centers with optical threshold near 2.7-2.8 eV and 3 eV often associated with C-related defects. However, no signals that could be attributed to substitutional C acceptors and C donors were detected. Current relaxation spectroscopy revealed deep traps with activation energies 0.2, 0.25, 045, and 0.8 eV. Annealing at 800 °C increased the concentration of these traps. The changes in resistivity induced by annealing in the high-growth rate sample were much stronger than for the low-temperature sample. The authors also observed a strong suppression of the yellow luminescence band intensity in the "standard" sample after annealing, as opposed to a slight increase of this band intensity in the two semi-insulating samples. The role of compensation by native defects and by deep levels related to carbon in the observed changes is discussed. © 2013 American Vacuum Society.


Crisman E.,University of Rhode Island | Drehman A.,Air Force Research Lab | Miller R.,Agnitron Technology Inc. | Osinsky A.,Agnitron Technology Inc. | And 2 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

Measurements of the pyroelectric coefficient and pyroelectric voltage response of polycrystalline AlN films are presented. The results were used to calculate pyroelectric detectivity figures of merit in order to compare potential AlN pyroelectric sensor performance to other pyroelectric materials such as epitaxial AlN, PbSc0.5Ta0.5O3, and Ba0.65Sr0.35TiO3 films. We observed substantial enhancement (∼5x) of pyroelectric coefficient and pyroelectric figure of merit in polycrystalline multi-oriented AlN films when compared to epitaxial monocrystalline AlN films. A mechanism of such augmentation in polycrystalline AlN films is proposed and discussed. Despite the relatively small absolute value of pyroelectric coefficient, AlN presents pyroelectric detectivity figure of merit near the same magnitude as commonly used pyroelectric materials because of its relatively low dielectric constant. The low dielectric constant enables high speed sensor operation >MHz. The results of these studies are suggesting even higher pyroelectric response might be obtainable for the polycrystalline thin film AlN structures. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wei M.,University of Central Florida | Casey Boutwell R.,University of Central Florida | Faleev N.,Arizona State University | Osinsky A.,Agnitron Technology Inc. | Schoenfeld W.V.,University of Central Florida
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures | Year: 2013

ZnO thin films were epitaxially grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. A low temperature homonucleation ZnO layer was found crucial at the interfacial region to absorb the defects formed by the lattice mismatch between the sapphire and ZnO, resulting in a smooth surface that enables smooth 2D epitaxial growth. High quality ZnO films were achieved after careful optimization of critical growth conditions: the sequence of Zn and O source shutters, growth temperature for both the ZnO nucleation and growth layer, and Zn/O ratio. Oxygen plasma pretreatment was not applied prior to the growth, thus shortening the growth time and reducing oxidation of the metallic sources. Resultant epitaxial ZnO films on sapphire demonstrated a root-mean-square surface roughness of 0.373nm for 1μm×1μm atomic force microscope images with clear hexagonal structure and terrace steps. The x-ray diffraction full width at half maximum (FWHM) for ω and ω-2θ ZnO (0002) triple-crystal rocking curves were measured to be 13 and 26 arc/s, respectively. This FWHM value is lower than any reported to date in the literature, with ω and ω-2θ values indicating excellent coherence of the epitaxial layer along the interface and the growth direction, accordingly. These x-ray diffraction and surface roughness values are lower than those obtained using common nucleation layers such as MgO, indicating that growth with ZnO nucleation layers on sapphire may lead to higher quality electrical and optical devices. © 2013 American Vacuum Society.


Grant
Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase II | Award Amount: 999.04K | Year: 2014

This project address the fabrication of solar blind detectors from the MgZnO material system. Both MBE and MOCVD material growth techniques will be used for deposition of the required material layers. Simulation software we be used to aid in the design of the photodetector structure. Devices will be fabricated from the grown structures and their electrical and optical characteristics determined.


Deen D.A.,Agnitron Technology Inc. | Osinsky A.,Agnitron Technology Inc. | Miller R.,Agnitron Technology Inc.
Applied Physics Letters | Year: 2014

A capacitive wireless sensing scheme is developed that utilizes an AlN/GaN-based dual-channel varactor. The dual-channel heterostructure affords two capacitance plateaus within the capacitance-voltage (CV) characteristic, owing to the two parallel two-dimensional electron gases (2DEGs) located at respective AlN/GaN interfaces. The capacitance plateaus are leveraged for the definition of two resonant states of the sensor when implemented in an inductively-coupled resonant LRC network for wireless readout. The physics-based CV model is compared with published experimental results, which serve as a basis for the sensor embodiment. The bimodal resonant sensor is befitting for a broad application space ranging from gas, electrostatic, and piezoelectric sensors to biological and chemical detection. © 2014 AIP Publishing LLC.


Grant
Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase I | Award Amount: 149.59K | Year: 2013

This Phase I program is focused on enhancement of the performance of MgZnO based solar blind detectors. MgZnO alloys have superior optoelectronic properties with bandgaps suitable for solar blind detection. Issues related to doping and miscibility will be addressed. This will involve the use of advanced MOCVD and MBE growth techniques and consideration of both Schottky and p-n junction devices. Novel doping strategies will be explored as well as the use of nearly lattice matched oxide substrates. Optimal device design will be achieved with the aid of simulation software. Detectors will be fabricated to demonstrate the feasibility of the technology. These robust, compact devices are sought as replacements for photomultiplier tubes in current use.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 124.93K | Year: 2014

This project is directed to the development of low-loss, high power-density Aluminum Nitride (AlN)/Gallium Nitride (GaN) heterostructure based transistors for enabling high-efficiency solid state power amplifiers (SSPA) needed for advancing capabilities of future robotic and human exploration spacecraft. The AlN/GaN heterostructure is a particularly attractive system for switch-mode applications due to the extremely high charge density, high electron mobility, high intrinsic breakdown field, and physical thinness achievable and has seen widespread investigation toward solid-state amplifiers in the recent years. However, very few innovations have been proposed with this heterostructure despite its expansive capacity for various creative device concepts. A new patent-pending multichannel AlN/GaN Field Screening High Electron Mobility Transistor (FS-HEMT) design is described. Preliminary experimental results are presented validating design principles that will eliminate current collapse phenomenon at X- and Ka-band frequencies that has plagues traditional HEMT designs and will ultimately deliver a low-loss switch-mode device.


Grant
Agency: National Science Foundation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2013

This Small Business Innovation Research (SBIR) Phase I project addresses the development of a novel technique for improving the efficiency of ultraviolet (UV) light emitting devices (LEDs). The UV LED fabrication process typically includes deposition of thin semiconductor films onto substrates that can be fabricated into devices. Traditionally, during the deposition process impurities are added to the semiconductor films to obtain the desired electrical properties. The introduction of the impurities, however, produces defects in the semiconductor materials that can limit the efficiency of the devices. The technique proposed in this project will modify the deposition process of the semiconductor films in order to obtain the desired electrical properties without the use of intentional impurities. This has the potential of producing much more efficient light emitters. The proposed technique has the added advantage of producing material whose electrical properties are less sensitive to temperature, which can prove useful for many applications. The composition of the semiconductor materials investigated in this project can be modified to produce LEDs capable of emitting light from the ultraviolet to visible range. A successful project will lead to an enabling technology for development of novel, high efficiency LEDs. The broader impacts/commercial potential of this project addresses the development of efficient light emitting semiconductor devices. Fundamental physical properties studied in this effort will enhance scientific and technological understanding of the nature of semiconductors. These advances may yield a new paradigm for functionalizing semiconductor materials for more efficient and higher performance optical and electronic devices. Possible applications for this technological advance include general room lighting, traffic lights, outdoor displays, automotive applications, water treatment, sterilization, and ultrahigh density optical storage systems. Moreover, the technique proposed in this work may lead to improvement in the performance of other microelectronic devices such as transistors, laser diodes, modulators and photodetectors. The proposed devices will enable unique high power and extreme temperature operation as the approach does not face the same limitations as currently used technology. Significant commercialization potential exists for the proposed technology on the basis of superior performing devices in the aforementioned categories.


Grant
Agency: NSF | Branch: Standard Grant | Program: | Phase: | Award Amount: 150.00K | Year: 2013

This Small Business Innovation Research (SBIR) Phase I project addresses the development of a novel technique for improving the efficiency of ultraviolet (UV) light emitting devices (LEDs). The UV LED fabrication process typically includes deposition of thin semiconductor films onto substrates that can be fabricated into devices. Traditionally, during the deposition process impurities are added to the semiconductor films to obtain the desired electrical properties. The introduction of the impurities, however, produces defects in the semiconductor materials that can limit the efficiency of the devices. The technique proposed in this project will modify the deposition process of the semiconductor films in order to obtain the desired electrical properties without the use of intentional impurities. This has the potential of producing much more efficient light emitters. The proposed technique has the added advantage of producing material whose electrical properties are less sensitive to temperature, which can prove useful for many applications. The composition of the semiconductor materials investigated in this project can be modified to produce LEDs capable of emitting light from the ultraviolet to visible range. A successful project will lead to an enabling technology for development of novel, high efficiency LEDs.

The broader impacts/commercial potential of this project addresses the development of efficient light emitting semiconductor devices. Fundamental physical properties studied in this effort will enhance scientific and technological understanding of the nature of semiconductors. These advances may yield a new paradigm for functionalizing semiconductor materials for more efficient and higher performance optical and electronic devices. Possible applications for this technological advance include general room lighting, traffic lights, outdoor displays, automotive applications, water treatment, sterilization, and ultrahigh density optical storage systems. Moreover, the technique proposed in this work may lead to improvement in the performance of other microelectronic devices such as transistors, laser diodes, modulators and photodetectors. The proposed devices will enable unique high power and extreme temperature operation as the approach does not face the same limitations as currently used technology. Significant commercialization potential exists for the proposed technology on the basis of superior performing devices in the aforementioned categories.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 79.96K | Year: 2016

Future DoD and Navy missions require advances in current high voltage power electronics technology as existing technology and even recent promising advances in Silicon Carbide and Gallium Nitride based materials lack fundamental material properties to deliver switching capabilities needed for future high power converter applications, advanced radar and propulsion systems. Much interest has been recently directed towards the wide bandgap oxide semiconductor -Ga2O3 for potential application in these areas as it exhibits extraordinary material properties potentially suiting it for high voltage applications due to its ability to withstand very large electric fields. In this program a team of world renowned MOCVD and oxide semiconductor experts have been assembled to provide a comprehensive analysis through modeling, simulation and experimentation of the unique process for epitaxial growth of -Ga2O3 by MOCVD with the intent to refine and outline techniques for offering comprehensive p- and n-type doping control as well as high quality crystal growth rates of 2-4+ microns/hr.

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