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A.I. Yakimov,V.V. Kirienko,A.A. Bloshkin,A.V. Dvurechenskii,D.E. Utkin 한국물리학회 2020 Current Applied Physics Vol.20 No.7
The paper is devoted to optical testing of mid-infrared Ge/Si photodetectors obtained by stacking of self-assembled Ge quantum dots in multilayer structures, which are near-field coupled to the adjacent nanoplasmonic arrays of subwavelength holes in metallic films. It is shown that photocurrent and near-field spectra consist of several sets of peaks, which are attributted to surface plasmon waves, localized surface plasmon modes or diffractive Rayleigh anomaly depending on the hole diameter and the angle of incidence θ. We find that for small holes the greatest contribution to the photocurrent enhancement is due to the excitation of the surface plasmonpolariton waves for all θ. As the hole diameter is increased and becomes comparable with the array periodicity, the normal-incident photoresponse improvement is provided by the Rayleigh anomaly. With the increase of incident angle, the photocurrent enhancement is supposed to arise from coupling of the localized shape resonance and propagating plasmon modes.
Polyakov, A.Y.,Jeon, D.W.,Govorkov, A.V.,Smirnov, N.B.,Sokolov, V.N.,Kozhukhova, E.A.,Yakimov, E.B.,Lee, I.H. Elsevier Sequoia 2013 Journal of alloys and compounds Vol.554 No.-
Nanopillar structures were prepared by dry etching of maskless epitaxial lateral overgrowth (MELO) GaN samples using a mask of Ni nanoparticles formed upon annealing thin Ni films deposited on top of SiO<SUB>2</SUB>/GaN. Under our experimental conditions the average nanopillars dimensions were close to 170nm, with the nanopillars density close to 10<SUP>9</SUP>cm<SUP>-2</SUP>. The nanopillars formation was random and not correlated with the threading dislocation density in MELO GaN, as evidenced by comparing the size and density of nanopillars in the wing and seed regions of MELO GaN differing in dislocation density by an order of magnitude. After dry etching the luminescent intensity of nanopillars became actually lower than the intensity from the unetched matrix due to the impact of defects introduced in the sidewalls during nanopillars formation. The intensity greatly increased, together with a decrease in the leakage current of Schottky diodes, after rapid thermal annealing of nanopillar structures at 900<SUP>o</SUP>C and further increased after additional etching in KOH solution. These changes are attributed to annealing of radiation defects introduced by dry etching and further removal of the damaged region by KOH etching. The results suggest that, in nanopillar structures produced by dry etching, some increase of internal quantum efficiency alongside improvement of light extraction efficiency are responsible for the observed luminescence intensity changes.
Quantum Barrier Growth Temperature Affects Deep Traps Spectra of InGaN Blue Light Emitting Diodes
Polyakov, A. Y.,Smirnov, N. B.,Shchemerov, I. V.,Yakimov, E. B.,Yakimov, E. E.,Kim, Kyu Cheol,Lee, In-Hwan The Electrochemical Society 2018 ECS journal of solid state science and technology Vol.7 No.5
<P>Electroluminescence (EL) efficiency, deep electron and hole traps spectra, microcathodoluminescence (MCL), electron beam induced current (EBIC) imaging, and MCL spectra were studied for blue GaN/InGaN multi-quantum-well (MQW) light emitting diodes differing by the temperature at which the GaN barriers of the MQW active region were grown. It was found that increasing the growth temperature from 850 to 920 degrees C very strongly suppressed the formation of deep electron traps with level at E-c-1 eV in the GaN barriers and of the hole traps with levels at E-v+0.7eV in InGaN QWs. The suppression of the formation of the E-c-1 eV electron trap, a known prominent nonradiative recombination center in n-GaN, improved the carrier injection efficiency into the InGaN QWs and increased the external quantum efficiency by about 9%. EBIC and MCL imaging showed that the density of threading dislocations and terminating them V-pits was relatively low and similar for both studied growth temperatures, close to 10(8) cm(-2) . The cross-sectional dimensions of the V-pits were measurably higher for increased growth temperature. However, the rather low dislocation density and rather high dimensions of the V-pits were believed to result in minor contribution of these defects to the observed EL efficiency changes. (C) 2018 The Electrochemical Society.</P>
Vergeles, P.S.,Orlov, V.I.,Polyakov, A.Y.,Yakimov, E.B.,Kim, Taehwan,Lee, In-Hwan Elsevier 2019 Journal of Alloys and Compounds Vol.776 No.-
<P><B>Abstract</B></P> <P>The recombination and optical properties of dislocations in GaN introduced at room temperature by applied stress have been studied. It is observed that under the application of local shear stress of a few tens of MPa the dislocation glide in the parallel to the surface basal planes and in the planes intersecting the surface is activated at room temperature. It is shown that dislocations of dislocation half-loops gliding in the planes intersecting the surface can demonstrate both radiative and nonradiative recombination. Basal plane dislocations are shown to increase the nonradiative recombination rate. It is observed that the low-energy electron beam irradiation stimulates the dislocation glide both in the basal plane and the planes inclined to the surface, this effect being weaker for the basal plane. The analysis of electron irradiation effect on the dislocation related cathodoluminescence band suggests that this band is due to recombination involving complexes of point defects. These complexes are believed to be generated by gliding of the dislocation segments emerging at the surface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Recombination properties of dislocations in GaN after a Vickers indentation are studied. </LI> <LI> Dislocation glide in the basal plane and planes inclined to the surface is activated at room temperatures. </LI> <LI> Dislocation half-loops gliding in the planes inclined to the surface demonstrate radiative recombination of charge carriers. </LI> <LI> Low-energy electron beam irradiation stimulates the dislocation glides. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>