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Terziyska P.T.,Lakehead University | Terziyska P.T.,Bulgarian Academy of Science | Butcher K.S.A.,Lakehead University | Butcher K.S.A.,MEAglow Ltd. | And 3 more authors.
Applied Surface Science | Year: 2015

Vertically oriented InN nanorods were grown on selective areas of unintentionally patterned c-oriented sapphire substrates exhibiting sharp needles that preferentially accommodate In-metal liquid droplets, using Migration Enhanced Afterglow (MEAglow) growth technique. We point out that the formation of AlN needles on selected areas can be reproduced intentionally by over-nitridation of unmasked areas of sapphire substrates. The liquid indium droplets serve as a self-catalyst and the nanorods grow from the supersaturated indium melt in the droplet in a vertical direction. X-ray diffraction measurements indicate the presence of hexagonal InN only, with preferred orientation along (0 0 0 1) crystal axis, and very good crystalline quality. The room temperature Raman spectrum shows the presence of the A1(TO), E2(high) and A1(LO) phonon modes of the hexagonal InN. © 2015 Elsevier B.V. All rights reserved.

Gergova R.,Lakehead University | Butcher K.S.A.,MEAglow Ltd. | Butcher K.S.A.,Leibniz Institute for Crystal Growth | Binsted P.W.,Lakehead University | Gogova D.,Leibniz Institute for Crystal Growth
Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures | Year: 2014

In this paper, the authors report on epitaxial thin InN layers grown on commercially available undoped GaN buffer layers and on Ga2O 3 interlayers produced by Migration-Enhanced Afterglow Epitaxy (MEAglow). The InN layers reported here, also grown by the MEAglow technique, are 100-200 nm thick and have a measured absorption edge between 1.3 and 1.95 eV. Advancements in the growth process have now allowed the authors to improve the InN layers so that the growth has excellent two-dimensional morphology. Scanning electron microscope images show that terracing is strongly evident for samples grown on GaN templates. Atomic force microscopy shows a maximum height of the steps of about 2 nm. For the samples grown on Ga2O 3, crystal quality is superior to InN grown on AlN buffers with similar thicknesses. X-ray diffraction ω-2θ measurements indicate a full width of half maximum (FWHM) of 342-389 arcseconds for these extremely thin layers; a good part of this x-ray diffraction FWHM is likely due to residual strain between the InN and GaN or between the InN and oxide. © 2014 American Vacuum Society.

Terziyska P.T.,Lakehead University | Butcher K.S.A.,Lakehead University | Butcher K.S.A.,MEAglow Ltd. | Gogova D.,Leibniz Institute for Crystal Growth | And 4 more authors.
Materials Letters | Year: 2013

Self-catalytic growth of InN nanopillars on (0001) sapphire is reported under In-rich conditions, using the Migration Enhanced Afterglow (MEAglow) growth technique. The nanopillars are up to 2 μm in length and 100-200 nm in diameter, terminated with an In-metal droplet on the top, with growth direction and preferred orientation along the InN c-axis. The shape of the nanopillars is cylindrical and their diameter is determined by the diameter of the In-metal droplet. X-ray diffraction measurements indicate the presence of both cubic and hexagonal InN, with very good crystalline quality. The room temperature Raman spectrum shows the presence of the A1(TO), E2(high) and A1(LO) phonon modes of the hexagonal InN. © 2013 Elsevier B.V.

Terziyska P.T.,Lakehead University | Butcher K.S.A.,Lakehead University | Butcher K.S.A.,MEAGlow Ltd. | Alexandrov D.,Lakehead University | Alexandrov D.,MEAGlow Ltd.
Applied Surface Science | Year: 2012

The purpose of this study was to detect the presence of excess Ga- or In-metal on the surface of GaN or InN epitaxial layers, using AFM 1 and nanoindentation. We ascertain that in this case AFM phase-contrast images could not be used for actual material composition distribution mapping due to the large topography variation of the surface. Force spectroscopy on droplets shows observable hysteresis between approach and retraction curves as well as the presence of adhesion forces on the retraction curves. This indicates the presence of compliant material - Ga- or In-metal in our case. Etching away these droplets with HCl solution confirmed their metallic consistence. The presence of In-metal is confirmed by XRD 2 measurements on the InN sample with the presence of the (1 0 1)In reflection plane peak, which disappears after etching. The method becomes extremely useful for detection of Ga-metal which cannot be detected by XRD. We have also observed that this technique is also able to identify the situation where a metal droplet is partially nitrided on the droplet surface, so that it cannot be removed by etching, a situation where the droplets presence might not otherwise be observed by phase-contrast measurements, or by other techniques. © 2012 Elsevier B.V.

Butcher K.S.A.,Lakehead University | Butcher K.S.A.,Meaglow Ltd. | Alexandrov D.,Lakehead University | Alexandrov D.,Meaglow Ltd. | And 3 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2012

Some initial results are presented for gallium nitride and indium nitride thin films grown on c-plane sapphire using a prototype migration enhanced afterglow (MEAglow) system. Smooth surfaces of less than 1 nm root mean square surface roughness have been achieved for both InN and GaN films at growth temperatures of 450-560 °C and 665 °C respectively. This result is attributed to the increased adatom diffusion length allowed for the metal species during the growth process. Thicker GaN layers can now be grown than those previously reported. For InN, an impressive full width half maximum value of 290 arcsec has been achieved for the (0002) reflection using ω-2θ X-ray diffraction scans. Greater progress has so far been achieved for the growth of InN films because of the relative ease with which thick layers of indium metal can be nitrided to form a good quality layer. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Menkad T.,Lakehead University | Alexandrov D.,Lakehead University | Alexandrov D.,Meaglow Ltd. | Butcher K.S.A.,Lakehead University | Butcher K.S.A.,Meaglow Ltd.
2012 25th IEEE Canadian Conference on Electrical and Computer Engineering: Vision for a Greener Future, CCECE 2012 | Year: 2012

A new analytical model for a two terminal metal-oxide-Gallium Nitride/Indium Gallium Nitride heterojunction structure is presented. This model characterizes the space charge layer created by electron tunneling in the structure's channel which is made of intrinsic Gallium Nitride. A one dimensional (1-D) analysis is adopted, and a set of hypotheses is stated to frame the present work. © 2012 IEEE.

Butcher K.S.A.,Lakehead University | Butcher K.S.A.,Meaglow Ltd | Alexandrov D.,Lakehead University | Alexandrov D.,Meaglow Ltd | And 4 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2012

InN thin films were grown by a new technique, migration enhanced afterglow (MEAglow), a chemical vapour deposition (CVD) form of migration enhanced epitaxy (MEE). Here we describe the apparatus used for this form of film deposition, which includes a scalable hollow cathode nitrogen plasma source. Initial film growth results for InN are also presented including atomic force microscopy (AFM) images that indicate step flow growth with samples having root mean square (RMS) surface roughness of as little as 0.103nm in some circumstances for film growth on sapphire substrates. X-ray diffraction (XRD) results are also provided for samples with a full width half maximum (FWHM) of the (0002) ω-2Theta; peak of as little as 290 arcsec. Low pressure conditions that can result in damage to the InN during growth are described. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Togtema G.,Lakehead University | Georgiev V.,Lakehead University | Georgieva D.,Lakehead University | Gergova R.,Lakehead University | And 4 more authors.
Solid-State Electronics | Year: 2014

This paper presents observations of a previously unidentified source of performance limitation for GaN-InGaN LED devices. While most studies focus on output saturation known as 'current droop' from InGaN layer effects, we show an alike influence from p-type GaN's inherent background electron concentration. p-GaN material was investigated to confirm that, even though the material had an excess of holes, the background electrons were indeed present and were influencing the charge flow across device electrodes. This current does not cross LED heterojunctions but rather drifts toward its proximal device electrode, causing a source of heating while providing no carriers for light emitting recombination. The effects of this current were explored in an LED configuration, whose output showed weak efficiency at very low biases in addition to that from current droop. While the shortcoming under small currents has previously been attributed to electron tunneling across the junction, we propose that the background electrons inside p-GaN could be another explanation. © 2014 Elsevier Ltd. All rights reserved.

Butcher K.S.A.,Macquarie University | Butcher K.S.A.,Meaglow Ltd. | Chen P.P.-T.,Macquarie University | Downes J.E.,Macquarie University
Applied Physics Letters | Year: 2012

For some InN films large amounts of excess nitrogen are seen at low growth temperatures. Recent studies have revised downward the defect formation energies for several forms of nitrogen rich point-defects in InN. Here we calculate an activation energy of 0.4 ± 0.1 eV for the thermally activated removal of much of the excess nitrogen, believed to be interstitial nitrogen. This low energy barrier is shown to support the case for a low defect formation energy of the same native defect, although it is pointed out that non-equilibrium plasma based conditions are required to reach these lower defect formation energies. © 2012 American Institute of Physics.

Hong Tran N.,McGill University | Huy Le B.,McGill University | Fan S.,McGill University | Zhao S.,McGill University | And 5 more authors.
Applied Physics Letters | Year: 2013

We report on a detailed study of the structural and optical properties of nonstoichiometric nitrogen-rich InN grown on sapphire substrates, by migration enhanced afterglow deposition. The samples were polycrystalline, with the presence of InN dots. Unusually strong photoluminescence emission was measured at cryogenic temperatures, with the peak energy at ∼0.68 eV. Detailed analysis further shows that the sample has very low residual electron density in the range of ∼1016 cm-3 at temperatures below 20 K. © 2013 AIP Publishing LLC.

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