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Title: InGaN: Direct correlation of nanoscopic morphology features with optical and structural properties

Abstract

A comprehensive study on the impact of growth modes on the structural and optical properties of thick InGaN layers suitable for photovoltaic application is presented. Samples grown by metalorganic vapour phase epitaxy with different growth rates and thicknesses have been analyzed. The application of slow growth rates result in smooth layers while higher growth rates induce a meandering surface morphology. Using low-temperature cathodoluminescence, a direct correlation of the morphology to local luminescent properties is obtained: the top of meandering structures reveals a spectrally red-shifted emission compared to the emission wavelength expected from the average indium content determined by X-ray diffraction. The origin of this shift is identified and explained by increased indium incorporation on top of the meander due to a spatially localized compositional pulling effect.

Authors:
 [1];  [2]; ; ;  [3]; ; ; ;  [1]; ;  [4]
  1. OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany)
  2. (Germany)
  3. Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Universitätsplatz 2, 39106 Magdeburg (Germany)
  4. GaN Device Technology, RWTH Aachen University, Sommerfeldstraße 24, 52074 Aachen (Germany)
Publication Date:
OSTI Identifier:
22310887
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CATHODOLUMINESCENCE; CORRELATIONS; CRYSTAL GROWTH; GALLIUM COMPOUNDS; INDIUM COMPOUNDS; LAYERS; NITROGEN COMPOUNDS; OPTICAL PROPERTIES; PHOTOVOLTAIC EFFECT; RED SHIFT; SURFACES; THICKNESS; VAPOR PHASE EPITAXY; WAVELENGTHS; X-RAY DIFFRACTION

Citation Formats

Koch, Holger, E-mail: holger.koch@osram-os.com, GaN Device Technology, RWTH Aachen University, Sommerfeldstraße 24, 52074 Aachen, Bertram, Frank, August, Olga, Christen, Jürgen, Pietzonka, Ines, Ahl, Jan-Philipp, Strassburg, Martin, Lugauer, Hans-Jürgen, Kalisch, Holger, and Vescan, Andrei. InGaN: Direct correlation of nanoscopic morphology features with optical and structural properties. United States: N. p., 2014. Web. doi:10.1063/1.4893663.
Koch, Holger, E-mail: holger.koch@osram-os.com, GaN Device Technology, RWTH Aachen University, Sommerfeldstraße 24, 52074 Aachen, Bertram, Frank, August, Olga, Christen, Jürgen, Pietzonka, Ines, Ahl, Jan-Philipp, Strassburg, Martin, Lugauer, Hans-Jürgen, Kalisch, Holger, & Vescan, Andrei. InGaN: Direct correlation of nanoscopic morphology features with optical and structural properties. United States. doi:10.1063/1.4893663.
Koch, Holger, E-mail: holger.koch@osram-os.com, GaN Device Technology, RWTH Aachen University, Sommerfeldstraße 24, 52074 Aachen, Bertram, Frank, August, Olga, Christen, Jürgen, Pietzonka, Ines, Ahl, Jan-Philipp, Strassburg, Martin, Lugauer, Hans-Jürgen, Kalisch, Holger, and Vescan, Andrei. Mon . "InGaN: Direct correlation of nanoscopic morphology features with optical and structural properties". United States. doi:10.1063/1.4893663.
@article{osti_22310887,
title = {InGaN: Direct correlation of nanoscopic morphology features with optical and structural properties},
author = {Koch, Holger, E-mail: holger.koch@osram-os.com and GaN Device Technology, RWTH Aachen University, Sommerfeldstraße 24, 52074 Aachen and Bertram, Frank and August, Olga and Christen, Jürgen and Pietzonka, Ines and Ahl, Jan-Philipp and Strassburg, Martin and Lugauer, Hans-Jürgen and Kalisch, Holger and Vescan, Andrei},
abstractNote = {A comprehensive study on the impact of growth modes on the structural and optical properties of thick InGaN layers suitable for photovoltaic application is presented. Samples grown by metalorganic vapour phase epitaxy with different growth rates and thicknesses have been analyzed. The application of slow growth rates result in smooth layers while higher growth rates induce a meandering surface morphology. Using low-temperature cathodoluminescence, a direct correlation of the morphology to local luminescent properties is obtained: the top of meandering structures reveals a spectrally red-shifted emission compared to the emission wavelength expected from the average indium content determined by X-ray diffraction. The origin of this shift is identified and explained by increased indium incorporation on top of the meander due to a spatially localized compositional pulling effect.},
doi = {10.1063/1.4893663},
journal = {Applied Physics Letters},
number = 7,
volume = 105,
place = {United States},
year = {Mon Aug 18 00:00:00 EDT 2014},
month = {Mon Aug 18 00:00:00 EDT 2014}
}
  • Cathodoluminescence (CL) characteristics on 30-period InGaN/GaN multiple quantum well (MQW) solar cell structures are investigated, revealing the relationship between optical and structural properties of the MQW structures with a large number of quantum wells. In the bottom MQW layers, a blueshift of CL peak along the growth direction is found and attributed to the decrease of indium content due to the compositional pulling effect. An obvious split of emission peak and a redshift of the main emission energy are found in the top MQW layers when the MQW grows above the critical layer thickness. They are attributed to the segregationmore » of In-rich InGaN clusters rather than the increase of indium content in quantum well layer. The MQW structure is identified to consist of two regions: a strained one in the bottom, where the indium content is gradually decreased, and a partly relaxed one in the top with segregated In-rich InGaN clusters.« less
  • InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaNmore » to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, {mu}-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.« less
  • InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaNmore » to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, {mu}-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.« less
  • The results of the study of structural and optical properties of short-period InGaN/GaN superlattices synthesized by MOCVD on sapphire substrates are presented. To form the superlattices, the method of periodic interruption of the growth of the InGaN layer with hydrogen supply into the reactor was used. It is shown that, with the use of the suggested method, an InGaN/GaN periodic structure with the developed interfaces and regions of joining the neighboring InGaN layers not correlated in a vertical direction is formed. The formation of such regions leads to a heavy dependence of the shape of the emission spectra of themore » super-lattices on the number of periods in the range of 400-470 nm.« less
  • Highlights: ► First report on InGaN NPs by chemical co-precipitation method. ► There is no phase separation in InGaN NPs. ► Both NPs are suitable for optoelectronic devices in the visible region. ► First experimental observation of phonon mode at 272 cm{sup −1} for GaN NPs. ► First report on μ-Raman analysis for InGaN NPs. -- Abstract: A facile method for the synthesis of gallium nitride (GaN) and indium gallium nitride (InGaN) nanoparticles (NPs) has been reported by simple chemical co-precipitation method. The average diameters of the GaN and InGaN NPs were 12 nm and 38 nm respectively. GaN NPsmore » show high crystalline quality with hexagonal structure while InGaN NPs exhibits some cubic inclusion by X-ray diffraction. Room-temperature photoluminescence analysis shows the near-band edge emission at 3.43 eV for GaN and a strong blue emission at 3.0 eV for In{sub 0.4}Ga{sub 0.6}N NPs. The E{sub 2}{sup H} phonon peaks from micro-Raman scattering at 567 cm{sup −1} for GaN and 564 cm{sup −1} for InGaN confirms the wurtzite nature of both the NPs. In addition, we have also assigned some other phonon modes of GaN associated with zone boundary K point of the Brillouin zone which is not experimentally observed for their bulk counterparts.« less