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Displaying 1 - 25 of 43

Raman spectroscopy based measurements of carrier concentration in n-type GaN nanowires grown by plasma-assisted molecular beam epitaxy

September 30, 2016
Author(s)
Lawrence H. Robins, Elizabeth Horneber, Norman A. Sanford, Kristine A. Bertness, John B. Schlager
The carrier concentration in ensembles of n-type GaN nanowires (NWs) grown by plasma-assisted molecular beam epitaxy was determined by curve-fitting analysis of Raman spectra, based on modeling of the carrier concentration dependence of the longitudinal

Studies of photoconductivity and FET behavior in examining drift mobility, surface depletion, and transient effects in Si-doped GaN nanowires examined in vacuum and air

May 3, 2013
Author(s)
Norman A. Sanford, Lawrence H. Robins, Paul T. Blanchard, K. Soria, B. Klein, Kristine A. Bertness, John B. Schlager, Aric W. Sanders
Variable intensity photoconductivity (PC) performed under vacuum at 325 nm was used to estimate drift mobility and negative surface charge density sigma for c-axis oriented Si-doped GaN nanowires (NWs). In this approach we assumed that sigma was

Improved Performance of Schottky Diodes on Pendeo-Epitaxial Gallium Nitride

September 1, 2008
Author(s)
Lawrence H. Robins, T Zheleva, M Derenge, D Ewing, P Shah, K Jones, U Lee
We designed experiments to investigate the role of the dislocation density on the performance of Schottky diodes fabricated on GaN material grown conventionally and by pendeo-epitaxy. Devices of varying geometries were fabricated on the low defect density

Steady-state and time-resolved photoluminescence from relaxed and strained GaN nanowires grown by catalyst-free molecular-beam epitaxy

June 24, 2008
Author(s)
John B. Schlager, Kristine A. Bertness, Paul T. Blanchard, Lawrence H. Robins, Alexana Roshko, Norman A. Sanford
We report steady-state and time-resolved photoluminescence (TRPL) measurements on individual GaN nanowires (6-20 micrometers in length, 30-940 nm in diameter) grown by nitrogen-plasma-assisted, catalyst-free MBE on Si(111) and dispersed onto fused quartz

Optical and structural study of GaN nanowires grown by catalyst-free molecular beam epitaxy. II. Sub-band-gap luminescence and electron irradiation effects

June 4, 2007
Author(s)
Larry Robins, Kristine A. Bertness, Joy Barker, Norman Sanford, John B. Schlager
GaN nanowires with diameters of 50-250nm, grown by catalyst-free molecular beam epitaxy, were characterized by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy at temperatures from 3 to 297 K. Both as-grown samples and dispersions of

Optical and Structural Study of GaN Nanowires Grown by Catalyst-Free MBE: (II) Defect-Related Luminescence and Electron-Beam Irradiation Effects

June 1, 2007
Author(s)
Lawrence H. Robins, Kristine A. Bertness, John G. Barker, Norman A. Sanford, John B. Schlager
GaN nanowires grown by catalyst free molecular beam epitaxy were characterized by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy at temperatures from 3 K to 295 K. Both as grown samples, which contained approximately vertically oriented

Biaxial Stress Dependence of AlxGa 1-x As Photoluminescence

January 13, 2007
Author(s)
Grady S. White, Albert J. Paul, Kristine A. Bertness, Lawrence H. Robins
A study was conducted of the room temperature photoluminescence behavior of AlxGa1-xAs as a function of tensile, equi-biaxial stress for x = 0, 0.198, 0.36, 0.498, and 0.809. The composition range included both the direct and the indirect band gap regions

Composition Standards for AlGaAs Epitaxial Layers

April 1, 2006
Author(s)
Kristine A. Bertness, Todd E. Harvey, C. M. Wang, Albert J. Paul, Larry Robins
Standard Reference Materials (SRMs) 2840 to 2843 are semiconductor material artifacts that consist of an epitaxial layer of AlxGa (1-x)As on a GaAs substrate. From the energy at the peak intensity in the photoluminescence (PL) spectrum, the composition of

High-accuracy determination of epitaxial AlGaAs composition with inductively coupled plasma optical emission spectroscopy

March 1, 2006
Author(s)
Kristine A. Bertness, C. M. Wang, Marc L. Salit, Gregory C. Turk, Therese A. Butler, Albert J. Paul, Larry Robins
Inductively coupled plasma optical emission spectroscopy is shown to confirm a recent correlation between photoluminescence (PL) peak energy for AlGaAs epitaxial films and the Al mole fraction x of those films. These two methods also agree within their

High Degree of Crystalline Perfection in Spontaneously Grown GaN Nanowires

January 1, 2006
Author(s)
Kristine A. Bertness, Alexana Roshko, Albert Davydov, Igor Levin, Mark D. Vaudin, Joy Barker, John B. Schlager, Norman Sanford, Larry Robins
We have grown a variety of isolated GaN nanowires using gas-source molecular beam epitaxy (MBE) and characterized their structural and optical properties. The nanowires have demonstrated a number of promising materials characteristics, including low defect

Composition and Carrier Concentration Dependence of the Electronic Structure of InyGa1-yAs1-xNx Films With Nitrogen Mole Fraction Less Than 0.012

November 1, 2005
Author(s)
Youn S. Kang, Lawrence H. Robins, Anthony Birdwell, Alexander J. Shapiro, W. R. Thurber, Mark D. Vaudin, M M. Fahmi, D Bryson, S N. Mohammad
The electronic structure of Si-doped InyGa1-yAs1-xNx films on GaAs substrates, grown bynitrogen-plasma-assisted molecular-beam epitaxy, was examined by photoreflectance PR spectroscopy at temperatures between 20 and 300 K. The films were approximately 0.5

Photoreflectance Study of the Electronic Structure of Si-Doped InyGa 1-y As 1-x N x Films With x

March 1, 2005
Author(s)
Youn S. Kang, Lawrence H. Robins, Anthony Birdwell, Alexander J. Shapiro, W. R. Thurber, Mark D. Vaudin, M M. Fahmi, D Bryson, S N. Mohammad
The electronic structure of Si-doped InyGa1-yAs1-xNx films on GaAs substrates, grown by nitrogen-plasma-assisted MBE, was examined by photoreflectance (PR) spectroscopy at temperatures between20 K and 300 K. The measured critical-point energies were