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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>
Effects of laterally overgrown n-GaN thickness on defect and deep level concentrations
Polyakov, A. Y.,Smirnov, N. B.,Govorkov, A. V.,Markov, A. V.,Yakimov, E. B.,Vergeles, P. S.,Lee, In-Hwan,Lee, Cheul Ro,Pearton, S. J. American Vacuum Society 2008 JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B - Vol.26 No.3