A5006230217- GaN-based semiconductor devices and materials
- Semiconductor materials and devices
- Ga2O3 and related materials
- ZnO doping and properties
- Silicon Carbide Semiconductor Technologies
- Metal and Thin Film Mechanics
- Graphene research and applications
- Semiconductor Quantum Structures and Devices
- Nanowire Synthesis and Applications
- Diamond and Carbon-based Materials Research
- Advanced Photocatalysis Techniques
- Acoustic Wave Resonator Technologies
- Photorefractive and Nonlinear Optics
- Thermal properties of materials
- Advancements in Semiconductor Devices and Circuit Design
- Photonic and Optical Devices
- 2D Materials and Applications
- Optical Coatings and Gratings
- Advanced Fiber Laser Technologies
- Thin-Film Transistor Technologies
- Electronic and Structural Properties of Oxides
- Semiconductor materials and interfaces
- Copper Interconnects and Reliability
- Photocathodes and Microchannel Plates
- Plasma Diagnostics and Applications
United States Naval Research Laboratory
2015-2024
Boston University
2022
Syntek Technologies (United States)
2022
SUNY Brockport
2022
University of Virginia
2021
Georgia Institute of Technology
2021
King Fahd University of Petroleum and Minerals
2021
University of New Mexico
2021
University of Illinois Urbana-Champaign
2021
United States Navy
2009-2020
We report the first observation of linear magnetoresistance (LMR) in multilayer epitaxial graphene grown on SiC. show that exhibits large LMR from 2.2 K up to room temperature and it can be best explained by a purely quantum mechanical model. attribute inhomogeneities epitaxially film. The magnitude suggests potential for novel applications areas such as high-density data storage magnetic sensors actuators.
To make graphene technologically viable, the transfer of films to substrates appropriate for specific applications is required. We demonstrate dry epitaxial (EG) from C-face 4H-SiC onto SiO2, GaN and Al2O3 using a thermal release tape. Subsequent Hall effect measurements illustrated that minimal degradation in carrier mobility was induced following process lithographically patterned devices. Correspondingly, large drop concentration observed process, supporting notion gradient density...
β-Ga(2)O(3) films grown on Al(2)O(3) by a metalorganic chemical vapor deposition technique were used to fabricate solar-blind photodetector with planar photoconductor structure. The crystal structure and quality of the analyzed using X-ray diffraction micro-Raman spectroscopy. Si ions introduced into thin ion implantation method activated an annealing process form Ohmic contact between Ti/Au electrode film. electrical conductivity was greatly improved subsequent activation ions....
We report on the development of a large-area few-layer graphene (FLG)—based transparent conductive electrode as current spreading layer for GaN-based ultraviolet (UV) light-emitting diodes (LEDs). Large-area FLG was deposited Cu using chemical vapor deposition (CVD) method and subsequently transferred to surface UV LED. light at peak 372 nm emitted through FLG-based electrode. The effects were clearly evident in both optical images electroluminescence (EL) current-voltage (I-V)...
Epitaxial graphene layers were grown on the C-face of 4H- and 6H-SiC using an argon-mediated growth process. Variations in temperature pressure found to dramatically affect morphological properties layers. The presence argon during slowed rate formation led observation islanding. similarity morphology islands continuous films indicated that island nucleation coalescence is mechanism for graphene.
A long-standing goal of GaN device research has been the development a reliable, well-controlled process for p-GaN formation by ion implantation. Results to date have indicated an activation 1% or less using high-temperature rapid thermal annealing (RTA) techniques and coimplantation. Although Mg is relatively deep acceptor, this still much than theoretically achievable value (8.2% based on 160 meV acceptor level). multicycle RTA presented that capable achieving up 8% Mg-implanted GaN. This...
AlGaN/GaN high electron mobility transistors grown on Si, SiC, and sapphire substrates were exposed to 2-MeV proton irradiation in incremental fluences up 6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The devices characterized initially after each by Hall dc I-V measurements probe the mechanisms associated with radiation-induced degradation failure. It was determined that...
Planar thin film β-Ga2O3 photodetectors were irradiated with 5 MeV protons at doses from 1013 to 1015 cm−2, and the resulting effects on photocurrent, responsivity, quantum efficiency, photo-to-dark current ratio 254 nm wavelength measured both 25 150 °C. The photocurrent increased dose due introduction of damage nonionizing energy loss by protons. total calculated vacancy concentration × 1017 cm−3 over range investigated. dark in proportion implant dose, leading a decrease current. induced...
The radiation tolerance of AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on quality, low threading dislocation density (TDD) ammonothermal GaN and hydride vapor phase epitaxy substrates was studied compared to the response devices SiC where TDD is 104 times higher. Hall transport measurements were performed as a function 2 MeV proton fluence. had no effect response. Comparing results with published data reveals that almost all irradiated GaN-based HEMTs respond damage...
AlGaN/GaN high-electron mobility transistor (HEMT) structures were grown by metal-organic chemical vapor deposition on SiC, hydride phase epitaxy (HVPE) GaN, and ammonothermal GaN substrates to achieve HEMTs with over five orders of magnitude variation in extended defect density. This enables a direct comparison the effect defects device performance best possible reliability. As-grown material was characterized atomic force microscopy, electron channeling contrast imaging, Raman...
We report the effects of GaN surface pretreatments on material and electrical properties Al2O3 dielectric deposited by atomic layer deposition (ALD). A was at different temperatures metal organic chemical vapor grown n-GaN that treated with either H2O2:H2SO4 (1:5, piranha), HCl:H2O (1:1, HCl), or HF:H2O HF) prior to deposition. The layers piranha- HF-treated were observed be uniformly smooth. piranha pretreatment resulted in lowest hysteresis. Pretreatment removes carbon hydroxylates...
High electron mobility transistors (HEMTs) based on the AlGaN/GaN heterostructure are excellent candidates for power switching applications due to high critical field of wide bandgap III-N materials. However, reduction drain current at bias is a recognized device problem dominated by self-heating processes in regimes [1]. Reducing HEMT channel temperature increases carrier mobility, decreases transition times, reduces losses, and ultimately improves converter efficiency. Despite attractive...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation N. Nepal, S. B. Qadri, J. K. Hite, A. Mahadik, M. Mastro, C. R. Eddy; Epitaxial growth of AlN films via plasma-assisted atomic layer epitaxy. Appl. Phys. Lett. 19 August 2013; 103 (8): 082110. https://doi.org/10.1063/1.4818792 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley...
Selectively activated p-type regions are necessary for many electronic devices that require planar processing. The standard process of implanting dopants, such as Mg, in GaN is notoriously more difficult than other material systems, the extremely high temperatures required to activate implanted Mg also damage surface. In this research, a novel annealing technique introduced purpose – symmetric multicycle rapid thermal (SMRTA). It shown SMRTA superior earlier developed (MRTA) terms...
Reduced performance in Gallium Nitride (GaN)-based high electron mobility transistors (HEMTs) as a result of self-heating has been well-documented. To mitigate this effect, the incorporation thermal conductivity diamond heat spreading films or substrates proposed. A mid-process integration scheme, termed "gate-after-diamond," is shown to improve budget for NCD deposition and enables scalable, large-area coating without degrading Schottky gate metal. The optimization process step presented...
GaN films were doped with Eu to a concentration of ∼0.12at.% during growth at 800°C by molecular beam epitaxy, the cell temperature held constant 470°C. All samples postannealed 675°C. The exhibited strong photoluminescence (PL) in red (622nm) whose absolute intensity was function Ga flux growth, which ranged from 3.0×10−7to5.4×10−7Torr. maximum PL obtained 3.6×10−7Torr. showed room ferromagnetism saturation magnetization ∼0.1–0.45emu∕cm3, consistent past reports where found be predominantly...
Gd + ions were implanted at total doses of 3–6×1014cm2 into single-crystal GaN or AlN epilayers grown on sapphire substrates and annealed 700–1000°C. The showed no detectable diffusion in either material after annealing, as measured by secondary ion mass spectrometry, corresponding to a coefficient &lt;8×10−12cm2s−1. Under all annealing conditions, x-ray diffraction shows the formation second phases. In case GaN, these include Gd3Ga2, GdN, Gd, while for only peaks are observed. Both show...
Selective p-type doping of Si-doped GaN by Mg ion implantation and multicycle rapid thermal annealing (MRTA) is demonstrated. Samples were capped AlN annealed in N2 overpressure at temperatures up to 1330°C. MRTA resulted a lower resistivity films, compared conventionally-annealed reference sample. acceptor activation for the sample was calculated using two-layer corrected Hall method be about 1% room temperature. Low temperature photoluminescence revealed donor-acceptor bound electron-hole...
InN thin films possessing either a novel cubic or hexagonal phase were grown by plasma-assisted atomic layer epitaxy on an a-plane sapphire, Si(111), and GaN/sapphire templates, simultaneously. Two ALE growth temperature windows found between 175–185 °C 220–260 °C, in which the process is self-limiting. In lower window, sapphire crystallized face-centered lattice with NaCl type structure, has never been previously reported. other substrates formed more common phase. higher all of The...
The first step of a multi-cycle rapid thermal annealing process was systematically studied. surface, structure, and optical properties Mg implanted GaN thin films annealed at temperatures ranging from 900 to 1200 °C were investigated by Raman spectroscopy, photoluminescence, UV-visible atomic force microscopy, Nomarski microscopy. are capped with two layers in-situ metal organic chemical vapor deposition -grown AlN in 24 bar N2 overpressure avoid decomposition. crystal quality the improves...
Gallium nitride (GaN) is a wide-bandgap semiconductor that useful for optoelectronics and high speed power electronics. Fabrication of GaN devices requires etching many processing steps. Gas phase thermal atomic-layer-controlled desirable damage-free isotropic etching. In this letter, the atomic layer (ALE) crystalline was demonstrated using sequential exposures XeF2 BCl3. ALE achieved with an etch rate 0.55 Å/cycle at 195 °C 20 s 40 mTorr BCl3 0.5 50 mTorr. At same reactant exposures, rates...
The realization of selectively implanted p-type regions in GaN as well an understanding processing effects that cause carrier type conversion are key enabling steps for vertical devices. Here, Schottky barrier diodes (SBDs) with edge termination formed by either a field plate or junction extension (JTE) achieved ion and symmetric multicycle rapid thermal annealing (SMRTA) presented. devices JTE exhibited substantially reduced leakage currents improved turn-on characteristics. This is...
Gallium nitride (GaN) has emerged as a quintessential wide band-gap semiconductor for an array of high-power and high-frequency electronic devices. The phonon thermal resistances that arise in GaN thin films can result detrimental performances these applications. In this work, we report on the conductivity submicrometer micrometer thick homoepitaxial grown via two different techniques (metal-organic chemical vapor deposition molecular beam epitaxy) measured (time domain thermoreflectance...