Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 11 of 11

Full-Text Articles in Physics

Review Article: Molecular Beam Epitaxy Of Lattice-Matched Inalas And Ingaas Layers On Inp (111)A, (111)B, And (110), Christopher D. Yerino, Baolai Liang, Diana L. Huffaker, Paul J. Simmonds, Minjoo Larry Lee Jan 2017

Review Article: Molecular Beam Epitaxy Of Lattice-Matched Inalas And Ingaas Layers On Inp (111)A, (111)B, And (110), Christopher D. Yerino, Baolai Liang, Diana L. Huffaker, Paul J. Simmonds, Minjoo Larry Lee

Physics Faculty Publications and Presentations

For more than 50 years, research into III–V compound semiconductors has focused almost exclusively on materials grown on (001)-oriented substrates. In part, this is due to the relative ease with which III–Vs can be grown on (001) surfaces. However, in recent years, a number of key technologies have emerged that could be realized, or vastly improved, by the ability to also grow high-quality III–Vs on (111)- or (110)-oriented substrates These applications include: next-generation field-effect transistors, novel quantum dots, entangled photon emitters, spintronics, topological insulators, and transition metal dichalcogenides. The first purpose of this paper is ...


Selective-Area Growth Of Heavily N–Doped Gaas Nanostubs On Si(001) By Molecular Beam Epitaxy, Yoon Jung Chang, Paul J. Simmonds, Brett Beekley, Mark S. Goorsky, Jason C.S. Woo Apr 2016

Selective-Area Growth Of Heavily N–Doped Gaas Nanostubs On Si(001) By Molecular Beam Epitaxy, Yoon Jung Chang, Paul J. Simmonds, Brett Beekley, Mark S. Goorsky, Jason C.S. Woo

Physics Faculty Publications and Presentations

Using an aspect ratio trapping technique, we demonstrate molecular beam epitaxy of GaAs nanostubs on Si(001) substrates. Nanoholes in a SiO2 mask act as a template for GaAs-on-Si selective-area growth(SAG) of nanostubs 120 nm tall and ≤100 nm in diameter. We investigate the influence of growthparameters including substrate temperature and growth rate on SAG. Optimizing these parameters results in complete selectivity with GaAsgrowth only on the exposed Si(001). Due to the confined-geometry, strain and defects in the GaAs nanostubs are restricted in lateral dimensions, and surface energy is further minimized. We assess the electrical properties of ...


Gasb Thermophotovoltaic Cells Grown On Gaas By Molecular Beam Epitaxy Using Interfacial Misfit Arrays, Bor-Chau Juang, Ramesh B. Laghumavarapu, Brandon J. Foggo, Paul J. Simmonds, Andrew Lin, Baolai Liang, Diana L. Huffaker Mar 2015

Gasb Thermophotovoltaic Cells Grown On Gaas By Molecular Beam Epitaxy Using Interfacial Misfit Arrays, Bor-Chau Juang, Ramesh B. Laghumavarapu, Brandon J. Foggo, Paul J. Simmonds, Andrew Lin, Baolai Liang, Diana L. Huffaker

Physics Faculty Publications and Presentations

There exists a long-term need for foreign substrates on which to grow GaSb-based optoelectronic devices. We address this need by using interfacial misfit arrays to grow GaSb-based thermophotovoltaic cells directly on GaAs (001) substrates and demonstrate promising performance. We compare these cells to control devices grown on GaSb substrates to assess device properties and material quality. The room temperature dark current densities show similar characteristics for both cells on GaAs and on GaSb. Under solar simulation the cells on GaAs exhibit an open-circuit voltage of 0.121 V and a short-circuit current density of 15.5 mA/cm2. In ...


Carrier Capture Dynamics Of Single Ingaas/Gaas Quantum-Dot Layers, Kripa N. Chauhan Jan 2013

Carrier Capture Dynamics Of Single Ingaas/Gaas Quantum-Dot Layers, Kripa N. Chauhan

All Physics Faculty Publications

Using 800 nm, 25-fs pulses from a mode locked Ti:Al2O3 laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In0.4Ga0.6As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140 fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated ...


Carrier Capture Dynamics Of Single Ingaas/Gaas Quantum-Dot Layers, K. N. Chauhaun, D. Mark Riffe, Addison E. Everett, D. J. Kim, H Yang, F. K. Shen Jan 2013

Carrier Capture Dynamics Of Single Ingaas/Gaas Quantum-Dot Layers, K. N. Chauhaun, D. Mark Riffe, Addison E. Everett, D. J. Kim, H Yang, F. K. Shen

All Physics Faculty Publications

Using 800nm, 25-fs pulses from a mode locked Ti:Al2O3 laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In0.4Ga0.6As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated with initial InGaAs thickness and annealing temperature. With increasing ...


Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers Jan 2012

Stable Highly Conductive Zno Via Reduction Of Zn Vacancies, David C. Look, Timothy C. Droubay, Scott A. Chambers

Physics Faculty Publications

Growth of Ga-doped ZnO by pulsed laser deposition at 200 °C in an ambient of Ar and H2produces a resistivity of 1.5 × 10−4 Ω-cm, stable to 500 °C. The resistivity can be further reduced to 1.2 × 10−4 Ω-cm by annealing on Zn foil, which reduces the compensating Zn-vacancy acceptor concentration NA to 5 × 1019 cm−3, only 3% of the Ga-donor concentration ND of 1.6 × 1021 cm−3, with ND and NA determined from a degenerate mobility theory. The plasmon-resonance wavelength is only 1060 nm, further bridging ...


Highly Conductive Zno Grown By Pulsed Laser Deposition In Pure Ar, Robin C. Scott, Kevin D. Leedy, Burhan Bayraktaroglu, David C. Look, Yong-Hang Zhang Aug 2010

Highly Conductive Zno Grown By Pulsed Laser Deposition In Pure Ar, Robin C. Scott, Kevin D. Leedy, Burhan Bayraktaroglu, David C. Look, Yong-Hang Zhang

Physics Faculty Publications

Ga-doped ZnO was deposited by pulsed laser deposition at 200 °C on SiO2/Si, Al2O3, or quartz in 10 mTorr of pure Ar. The as-grown, bulk resistivity at 300 K is 1.8×10−4 Ω cm, three-times lower than that of films deposited at 200 °C in 10 mTorr of O2 followed by an anneal at 400 °C in forming gas. Furthermore, depth uniformity of the electrical properties is much improved. Mobility analysis shows that this excellent resistivity is mostly due to an increase in donor concentration, rather than a decrease in acceptor concentration ...


Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu Feb 2010

Mobility Analysis Of Highly Conducting Thin Films: Application To Zno, David C. Look, K. D. Leedy, D. H. Tomich, B. Bayraktaroglu

Physics Faculty Publications

Hall-effect measurements have been performed on a series of highly conductive thin films of Ga-doped ZnO grown by pulsed laser deposition and annealed in a forming-gas atmosphere (5% H2 in Ar). The mobility as a function of thickness d is analyzed by a simple formula involving only ionized-impurity and boundary scattering and having a single fitting parameter, the acceptor/donor concentration ratio K = NA/ND. For samples with d = 3–100 nm, Kavg = 0.41, giving ND = 4.7×1020 and NA = 1.9×1020 cm−3. Thicker samples require a two-layer ...


Electron And Hole Traps In N-Doped Zno Grown On P-Type Si Substrate By Mocvd, Zhaoqiang Fang, Bruce B. Claflin, David C. Look, Lei L. Kerr, Xiaonan Li Jan 2007

Electron And Hole Traps In N-Doped Zno Grown On P-Type Si Substrate By Mocvd, Zhaoqiang Fang, Bruce B. Claflin, David C. Look, Lei L. Kerr, Xiaonan Li

Physics Faculty Publications

Electron and hole traps in N-doped ZnO were investigated using a structure of n+-ZnO:Al/i-ZnO/ZnO:N grown on a p-Si substrate by metalorganic chemical vapor deposition (for growth of the ZnO:N layer) and sputtering deposition (for growth of the i-ZnO and n+-ZnO:Al layers). Current-voltage and capacitance-voltage characteristics measured at temperatures from 200 to 400 K show that the structure is an abrupt n+p diode with very low leakage currents. By using deep level transient spectroscopy, two hole traps, H3 (0.35 eV) and H4 (0.48 eV), are found in ...


Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester Jan 2004

Chemistry-Induced Intrinsic Stress Variations During The Chemical Vapor Deposition Of Polycrystalline Diamond, Ashok Rajamani, Brian W. Sheldon, Sumit Nijhawan, Alan Schwartzman, Janet Rankin, Barbara L. Walden, Laura Riester

Faculty Scholarship

Intrinsic tensile stresses in polycrystalline films are often attributed to the coalescence of neighboring grains during the early stages of film growth, where the energy decrease associated with converting two free surfaces into a grain boundary provides the driving force for creating tensile stress. Several recent models have analyzed this energy trade off to establish relationships between the stress and the surface∕interfacial energy driving force, the elastic properties of the film, and the grain size. To investigate these predictions, experiments were conducted with diamond films produced by chemical vapor deposition. A multistep processing procedure was used to produce films ...


Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look Dec 2000

Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look

Physics Faculty Publications

We have investigated the structural and optical properties of Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy. The carrier concentration in Ga-doped ZnO films can be controlled from 1.33×1018/cm3 to 1.13×1020/cm3. Despite high Ga incorporation, the linewidth of (0002) ω-rocking curves of Ga-doped ZnO films still lies in the range from 5 to 15 arc min. Photoluminescence (PL) spectra of Ga-doped ZnO films show dominant near-bandedge emission with negligibly weak deep-level emission, independent of carrier concentration. The PL spectrum exhibits a new emission line at 3.358 ...