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Search Publications by: Matthew Brubaker (Fed)

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Displaying 1 - 25 of 79

Semiconductor thermal and electrical properties decoupled by localized phonon resonances

May 10, 2023
Author(s)
Bryan Spann, Joel Weber, Matthew Brubaker, Todd E. Harvey, LINA YANG, Hossein Honarvar, Chia-Nien Tsai, Andrew Treglia, MINHYEA LEE, MAHMOUD HUSSEIN, Kris A. Bertness
Thermoelectric materials convert heat into electricity through thermally driven charge transport in solids or vice versa for cooling. To compete with conventional energy-conversion technologies, a thermoelectric material must possess the properties of both

Crystallographic Polarity Measurements in Two-Terminal GaN Nanowire Devices by Lateral Piezoresponse Force Microscopy

July 23, 2020
Author(s)
Matthew Brubaker, Alexana Roshko, Samuel Berweger, Paul T. Blanchard, Todd E. Harvey, Norman A. Sanford, Kris A. Bertness
Lateral piezoresponse force microscopy (L-PFM) is demonstrated as a reliable method for determining the crystallographic polarity of individual, dispersed GaN nanowires that were functional components in electrical test structures. In contrast to PFM

AlGaN/GaN core-shell heterostructures for nanowire UV LEDs

May 1, 2020
Author(s)
Matthew D. Brubaker, Bryan T. Spann, Kristen L. Genter, Alexana Roshko, Paul T. Blanchard, Todd E. Harvey, Kristine A. Bertness
Nanowire-based ultraviolet (UV) LEDs hold great promise as nanoscale light sources, potentially enabling advanced scanning microscopy probes capable of optoelectronic sensing and near-field scanning photolithography. In this work, we report on the

Eutectic Formation, V/III Ratio and Controlled Polarity Inversion in Nitrides on Silicon

November 19, 2019
Author(s)
Alexana Roshko, Matthew D. Brubaker, Paul T. Blanchard, Todd E. Harvey, Kristine A. Bertness
The crystallographic polarity of AlN grown on Si(111) by plasma assisted molecular beam epitaxy is intentionally inverted from N-polar to Al-polar at a planar boundary. The position of the inversion boundary is controlled by a two-step growth process that

The role of Si in GaN/AlN/Si(111) PAMBE Epitaxy: Polarity and Inversion

May 22, 2019
Author(s)
Alexana Roshko, Matthew D. Brubaker, Paul T. Blanchard, Todd E. Harvey, Kristine A. Bertness
The microstructure, polarity and Si distribution in AlN/GaN layers grown by PAMBE on Si(111) was assessed by STEM. Samples grown under both metal- and nitrogen-rich conditions contained defects at the AlN/Si interface which suggest formation of an Al-Si

UV LEDs Based on p-i-n Core-Shell AlGaN/GaN Nanowire Heterostructures Grown by N-polar Selective Area Epitaxy

March 20, 2019
Author(s)
Matthew Brubaker, Kristen Genter, Alexana Roshko, Paul T. Blanchard, Bryan T. Spann, Todd E. Harvey, Kris A. Bertness
Ultraviolet light-emitting diodes (UV LEDs) fabricated from N-polar AlGaN/GaN core-shell nanowires with p-i-n structure produced electroluminescence at 365 nm with 5x higher intensities than similar GaN homojunction LEDs. The improved characteristics were

Axisymmetric scalable magneto-gravitational trap for diamagnetic particle levitation

December 11, 2018
Author(s)
Kristine A. Bertness, John P. Houlton, Max L. Chen, Matthew D. Brubaker, Charles T. Rogers
We report an axisymmetric magnetic trap design for levitating diamagnetic particles. The magnetic traps each consist of two iron pole pieces passively driven by a neodymium iron boron (NdFeB) permanent magnet. The magnetic field configuration between the

An optical Bragg scattering readout for simultaneous detection of all low-order mechanical modes of gallium nitride nanowires in nanowire arrays

September 19, 2018
Author(s)
Kristine A. Bertness, John P. Houlton, Matthew D. Brubaker, Charles T. Rogers
We report the use of optical Bragg scattering and homodyne interferometry to simultaneously measure all the first order cantilever-mode mechanical resonance frequencies and quality factors (Q) of gallium nitride nanowires (GaN NWs) in 100 NW periodic

Core-Shell p-i-n GaN Nanowire LEDs by N-polar Selective Area Growth

September 11, 2018
Author(s)
Matthew D. Brubaker, Kristen L. Genter, Bryan T. Spann, Alexana Roshko, Paul T. Blanchard, Todd E. Harvey, Kristine A. Bertness
GaN nanowire LEDs with radial p-i-n junctions were grown by molecular beam epitaxy using N- polar selective area growth on Si(111) substrates. The N-polar selective area growth process facilitated the growth of isolated and high-aspect-ratio n-type NW