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Full-Text Articles in Physics
Deep Traps In Algan/Gan Heterostructures Studied By Deep Level Transient Spectroscopy: Effect Of Carbon Concentration In Gan Buffer Layers, Z-Q. Fang, B. Claflin, David C. Look, D. S. Green, R. Vetury
Deep Traps In Algan/Gan Heterostructures Studied By Deep Level Transient Spectroscopy: Effect Of Carbon Concentration In Gan Buffer Layers, Z-Q. Fang, B. Claflin, David C. Look, D. S. Green, R. Vetury
Physics Faculty Publications
Electrical properties, including leakage currents, threshold voltages, and deep traps, of AlGaN/GaN heterostructure wafers with different concentrations of carbon in the GaN buffer layer, have been investigated by temperature dependent current-voltage and capacitance-voltage measurements and deep level transient spectroscopy (DLTS), using Schottky barrier diodes (SBDs). It is found that (i) SBDs fabricated on the wafers with GaN buffer layers containing a low concentration of carbon (low-[C] SBD) or a high concentration of carbon (high-[C] SBD) have similar low leakage currents even at 500 K; and (ii) the low-[C] SBD exhibits a larger (negative) threshold voltage than the high-[C] SBD. Detailed …
Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffman, John R. Dennison, Clint D. Thomson, Jennifer Albresten
Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffman, John R. Dennison, Clint D. Thomson, Jennifer Albresten
All Physics Faculty Publications
Electron-induced electron yields of high-resistivity high-yield materials - ceramic polycrystalline aluminum oxide and polymer polyimide (Kapton HN) - were made by using a low-fluence pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in the energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of < 3 fC/mm2. The evolution of the electron yield as charge accumulates in the material is modeled in terms of electron recapture based on an extended Chung-Everhart model of the electron emission spectrum. This model is used to explain the anomalies measured in highly …
The Temperature Dependence Of Hysteretic Processes In Co Nanowires Arrays, I Astefanoaei, I Dumitru, A Diaconu, L Spinu, A Stancu
The Temperature Dependence Of Hysteretic Processes In Co Nanowires Arrays, I Astefanoaei, I Dumitru, A Diaconu, L Spinu, A Stancu
Physics Faculty Publications
In this paper, the temperature dependence of the hysteretic processes of Co nanowires, squarelly ordered in an array prepared by electrodeposition in nanopores of alumina membranes was analyzed. Both the magnetostatic interactions induced in the nanowires arrays and the thermal stresses (radial, azimuthal and axial stresses), which appear during the cooling of the system (nanowire and alumina template) from room temperature to 3 K was evaluated. The analysis of thermal induced stresses provides useful informations concerning the magnetic anisotropy in the Co nanowires. The temperature dependence of the remanent magnetization and coercitive field as an effect of the induced thermal …
Nonlinear All-Optical Gan/Algan Multi-Quantum-Well Devices For 100 Gb/S Applications At Λ = 1.55 Μm, Greg Sun, Jacob B. Khurgin, Richard A. Soref
Nonlinear All-Optical Gan/Algan Multi-Quantum-Well Devices For 100 Gb/S Applications At Λ = 1.55 Μm, Greg Sun, Jacob B. Khurgin, Richard A. Soref
Physics Faculty Publications
Using quantum-mechanical analysis, a strain-balanced stack of coupled GaN/AlGaNquantum wells has been engineered for bandwidth-optimized all-optical switching at low switching powers. Intersubband transitions between three conduction subbands provide the basis for the large, fast, nonlinear optical response. Optimized performance for a given symbol rate is obtained by engineering the response time and nonlinear phase shift.
Half-Metallicity And Efficient Spin Injection In Aln/Gan:Cr (0001) Heterostructure, Julia E. Medvedeva, X. Y. Cui, C. Stampfl, N. Newman, Arthur J. Freeman
Half-Metallicity And Efficient Spin Injection In Aln/Gan:Cr (0001) Heterostructure, Julia E. Medvedeva, X. Y. Cui, C. Stampfl, N. Newman, Arthur J. Freeman
Physics Faculty Research & Creative Works
First-principles investigations of the structural, electronic, and magnetic properties of Cr-doped AlN/GaN (0001) heterostructures reveal the possibility of efficient spin injection from a ferromagnetic GaN:Cr electrode through an AlN tunnel barrier. We demonstrate that Cr atoms segregate into the GaN region and that these interfaces retain their half-metallic behavior leading to a complete, i.e., 100%, spin polarization of the conduction electrons. This property makes the wide band-gap nitrides doped with Cr to be excellent candidates for high-efficiency magnetoelectronic devices.
Reduced Threshold Current Of A Quantum Dot Laser In A Short Period Superlattice Of Indirect-Band Gap, Greg Sun, Richard A. Soref, Jacob B. Khurgin
Reduced Threshold Current Of A Quantum Dot Laser In A Short Period Superlattice Of Indirect-Band Gap, Greg Sun, Richard A. Soref, Jacob B. Khurgin
Physics Faculty Publications
We propose the idea of making quantum dot lasers by embedding direct-band gap quantum dots in a short period superlattice whose band gap is indirect. This technique reduces the threshold current and its temperature dependence. We show that a higher characteristic-temperature T0 can be achieved in a quantum dot laser with indirect GaAs/AlAs superlattice barriers compared to that with direct GaAs barriers.
Phonon-Pumped Terahertz Gain In N-Type Gaas/Algaas Superlattices, Greg Sun, Richard A. Soref
Phonon-Pumped Terahertz Gain In N-Type Gaas/Algaas Superlattices, Greg Sun, Richard A. Soref
Physics Faculty Publications
Local population inversion and far-IR gain are proposed and theoretically analyzed for an unbiased n-doped GaAs/Al0.15Ga0.85As superlattice pumped solely by phonons. The lasing transition occurs at the Brillouin zone boundary of the superlattice wave vector kzbetween the two conduction minibands CB1 and CB2 of the opposite curvature in kzspace. The proposed waveguided structure is contacted above and below by heat sinks at 300 K and 77 K, respectively. Atop the superlattice, a heat buffer layer confines longitudinal optical phonons for enhanced optical-phonon pumping of CB1 electrons. A gain of 345 cm …