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Title: High pressure and time resolved studies of optical properties of n-type doped GaN/AlN multi-quantum wells: Experimental and theoretical analysis

Abstract

High-pressure and time-resolved studies of the optical emission from n-type doped GaN/AlN multi-quantum-wells (MQWs) with various well thicknesses are analysed in comparison with ab initio calculations of the electronic (band structure, density of states) and optical (emission energies and their pressure derivatives, oscillator strength) properties. The optical properties of GaN/AlN MQWs are strongly affected by quantum confinement and polarization-induced electric fields. Thus, the photoluminescence (PL) peak energy decreases by over 1 eV with quantum well (QW) thicknesses increasing from 1 to 6 nm. Furthermore, the respective PL decay times increased from about 1 ns up to 10 μs, due to the strong built-in electric field. It was also shown that the band gap pressure coefficients are significantly reduced in MQWs as compared to bulk AlN and GaN crystals. Such coefficients are strongly dependent on the geometric factors such as the thickness of the wells and barriers. The transition energies, their oscillator strength, and pressure dependence are modeled for tetragonally strained structures of the same geometry using a full tensorial representation of the strain in the MQWs under external pressure. These MQWs were simulated directly using density functional theory calculations, taking into account two different systems: the semi-insulating QWs and the n-doped QWs with themore » same charge density as in the experimental samples. Such an approach allowed an assessment of the impact of n-type doping on optical properties of GaN/AlN MQWs. We find a good agreement between these two approaches and between theory and experimental results. We can therefore confirm that the nonlinear effects induced by the tetragonal strain related to the lattice mismatch between the substrates and the polar MQWs are responsible for the drastic decrease of the pressure coefficients observed experimentally.« less

Authors:
 [1];  [2]; ;  [1]; ; ; ;  [3];  [4]; ;  [5];  [6];  [1];  [2]
  1. Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw (Poland)
  2. (Poland)
  3. Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland)
  4. University of Warsaw, Faculty of Physics, Pasteura 5, 02-093 Warsaw (Poland)
  5. Université Grenoble-Alpes, 38000 Grenoble (France)
  6. (France)
Publication Date:
OSTI Identifier:
22598822
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 120; Journal Issue: 9; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM NITRIDES; COMPARATIVE EVALUATIONS; CRYSTAL DEFECTS; CRYSTALS; DENSITY FUNCTIONAL METHOD; DENSITY OF STATES; DOPED MATERIALS; ELECTRIC FIELDS; GALLIUM NITRIDES; NONLINEAR PROBLEMS; N-TYPE CONDUCTORS; OPTICAL PROPERTIES; OSCILLATORS; PHOTOLUMINESCENCE; PRESSURE COEFFICIENT; PRESSURE DEPENDENCE; QUANTUM WELLS; THICKNESS; TIME RESOLUTION

Citation Formats

Kaminska, A., Cardinal Stefan Wyszynski University, College of Science, Department of Mathematics and Natural Sciences, Dewajtis 5, 01-815 Warsaw, Jankowski, D., Sobczak, K., Strak, P., Sakowski, K., Grzanka, E., Krukowski, S., Korona, K. P., Beeler, M., Monroy, E., CEA Grenoble, INAC-PHELIQS, 17 av. des Martyrs, 38000 Grenoble, Borysiuk, J., and University of Warsaw, Faculty of Physics, Pasteura 5, 02-093 Warsaw. High pressure and time resolved studies of optical properties of n-type doped GaN/AlN multi-quantum wells: Experimental and theoretical analysis. United States: N. p., 2016. Web. doi:10.1063/1.4962282.
Kaminska, A., Cardinal Stefan Wyszynski University, College of Science, Department of Mathematics and Natural Sciences, Dewajtis 5, 01-815 Warsaw, Jankowski, D., Sobczak, K., Strak, P., Sakowski, K., Grzanka, E., Krukowski, S., Korona, K. P., Beeler, M., Monroy, E., CEA Grenoble, INAC-PHELIQS, 17 av. des Martyrs, 38000 Grenoble, Borysiuk, J., & University of Warsaw, Faculty of Physics, Pasteura 5, 02-093 Warsaw. High pressure and time resolved studies of optical properties of n-type doped GaN/AlN multi-quantum wells: Experimental and theoretical analysis. United States. doi:10.1063/1.4962282.
Kaminska, A., Cardinal Stefan Wyszynski University, College of Science, Department of Mathematics and Natural Sciences, Dewajtis 5, 01-815 Warsaw, Jankowski, D., Sobczak, K., Strak, P., Sakowski, K., Grzanka, E., Krukowski, S., Korona, K. P., Beeler, M., Monroy, E., CEA Grenoble, INAC-PHELIQS, 17 av. des Martyrs, 38000 Grenoble, Borysiuk, J., and University of Warsaw, Faculty of Physics, Pasteura 5, 02-093 Warsaw. Wed . "High pressure and time resolved studies of optical properties of n-type doped GaN/AlN multi-quantum wells: Experimental and theoretical analysis". United States. doi:10.1063/1.4962282.
@article{osti_22598822,
title = {High pressure and time resolved studies of optical properties of n-type doped GaN/AlN multi-quantum wells: Experimental and theoretical analysis},
author = {Kaminska, A. and Cardinal Stefan Wyszynski University, College of Science, Department of Mathematics and Natural Sciences, Dewajtis 5, 01-815 Warsaw and Jankowski, D. and Sobczak, K. and Strak, P. and Sakowski, K. and Grzanka, E. and Krukowski, S. and Korona, K. P. and Beeler, M. and Monroy, E. and CEA Grenoble, INAC-PHELIQS, 17 av. des Martyrs, 38000 Grenoble and Borysiuk, J. and University of Warsaw, Faculty of Physics, Pasteura 5, 02-093 Warsaw},
abstractNote = {High-pressure and time-resolved studies of the optical emission from n-type doped GaN/AlN multi-quantum-wells (MQWs) with various well thicknesses are analysed in comparison with ab initio calculations of the electronic (band structure, density of states) and optical (emission energies and their pressure derivatives, oscillator strength) properties. The optical properties of GaN/AlN MQWs are strongly affected by quantum confinement and polarization-induced electric fields. Thus, the photoluminescence (PL) peak energy decreases by over 1 eV with quantum well (QW) thicknesses increasing from 1 to 6 nm. Furthermore, the respective PL decay times increased from about 1 ns up to 10 μs, due to the strong built-in electric field. It was also shown that the band gap pressure coefficients are significantly reduced in MQWs as compared to bulk AlN and GaN crystals. Such coefficients are strongly dependent on the geometric factors such as the thickness of the wells and barriers. The transition energies, their oscillator strength, and pressure dependence are modeled for tetragonally strained structures of the same geometry using a full tensorial representation of the strain in the MQWs under external pressure. These MQWs were simulated directly using density functional theory calculations, taking into account two different systems: the semi-insulating QWs and the n-doped QWs with the same charge density as in the experimental samples. Such an approach allowed an assessment of the impact of n-type doping on optical properties of GaN/AlN MQWs. We find a good agreement between these two approaches and between theory and experimental results. We can therefore confirm that the nonlinear effects induced by the tetragonal strain related to the lattice mismatch between the substrates and the polar MQWs are responsible for the drastic decrease of the pressure coefficients observed experimentally.},
doi = {10.1063/1.4962282},
journal = {Journal of Applied Physics},
number = 9,
volume = 120,
place = {United States},
year = {Wed Sep 07 00:00:00 EDT 2016},
month = {Wed Sep 07 00:00:00 EDT 2016}
}
  • The results of comprehensive theoretical and experimental study of binary GaN/AlN multi-quantum well (MQW) systems oriented along polar c-direction of their wurtzite structure are presented. A series of structures with quantum wells and barriers of various thicknesses were grown by plasma-assisted molecular-beam epitaxy and characterized by x-ray diffraction and transmission electron microscopy. It was shown that in general the structures of good quality were obtained, with the defect density decreasing with increasing quantum well thickness. The optical transition energies in these structures were investigated comparing experimental measurements with ab initio calculations of the entire GaN/AlN MQW structure depending on themore » QW widths and strains, allowing for direct determination of the energies of optical transitions and the electric fields in wells/barriers by electric potential double averaging procedure. Photoluminescence (PL) measurements revealed that the emission efficiency as well as the shape of luminescence spectra correlated well with their structural quality. Additionally, due to the Quantum-Confined Stark Effect, the emission energy decreased by over 1 eV for quantum well thicknesses increasing from 1 nm up to 6 nm, and this effect was accompanied by the drastic drop of the PL efficiency. The experimental results are consistent with theoretical models. Comparison of experimental data obtained by a number of different characterization techniques with the density functional theory results received on the same geometry structure allowed to prove directly the theoretical models and to determine the polarization and the oscillator strengths in the AlN/GaN nitride systems for the first time.« less
  • AlN/GaN multiple quantum wells (MQWs) with a well thickness of 26 Aa have been grown by metal{endash}organic chemical-vapor deposition. A specially designed photoluminescence (PL) spectroscopy system, which is capable of measuring picosecond time-resolved PL up to 6.2 eV, has been employed to probe the optical properties as well as the carrier transfer and decay dynamics in these MQWs. Optical transitions at 4.039 and 5.371 eV at T=10 K, resulting from the interband recombination between the electrons and holes in the n=1 and n=2 subbands in the wells, have been observed. The band-offset parameter for the AlN/GaN heterostructure has been obtainedmore » by comparing the experimental results with the calculations. Carrier dynamics including the relaxation of the electrons and holes from the n=2 and n=1 subband in the conduction and valence bands and the decay lifetimes of the interband transitions have also been measured and analyzed. Detailed subband structures for both the conduction and valence bands in the wells were determined. The implications of our findings on the potential applications of AlN/GaN quantum wells have been discussed. {copyright} 2001 American Institute of Physics.« less
  • This work shows that the combination of ultrathin highly strained GaN quantum wells embedded in an AlN matrix, with controlled isotopic concentrations of Nitrogen enables a dual marker method for Raman spectroscopy. By combining these techniques, we demonstrate the effectiveness in studying strain in the vertical direction. This technique will enable the precise probing of properties of buried active layers in heterostructures, and can be extended in the future to vertical devices such as those used for optical emitters and for power electronics.
  • The optical and structural properties of InGaN/GaN multi-quantum wells (MQWs) with different thicknesses of low temperature grown GaN cap layers are investigated. It is found that the MQW emission energy red-shifts and the peak intensity decreases with increasing GaN cap layer thickness, which may be partly caused by increased floating indium atoms accumulated at quantum well (QW) surface. They will result in the increased interface roughness, higher defect density, and even lead to a thermal degradation of QW layers. An extra growth interruption introduced before the growth of GaN cap layer can help with evaporating the floating indium atoms, andmore » therefore is an effective method to improve the optical properties of high indium content InGaN/GaN MQWs.« less
  • The optical properties and coupling of excitons to surface plasmon polaritons (SPPs) in Ag, Au, and Al-coated In{sub x}Ga{sub 1−x}N/GaN multiple and single quantum wells (SQWs) were probed with time-resolved cathodoluminescence. Excitons were generated in the metal coated SQWs by injecting a pulsed high-energy electron beam through the thin metal films. The Purcell enhancement factor (F{sub p}) was obtained by direct measurement of changes in the temperature-dependent radiative lifetime caused by the SQW exciton-SPP coupling. Three chosen plasmonic metals of Al, Ag, and Au facilitate an interesting comparison of the exciton-SPP coupling for energy ranges in which the SP energymore » is greater than, approximately equal to, and less than the excitonic transition energy for the InGaN/GaN QW emitter. A modeling of the temperature dependence of the Purcell enhancement factor, F{sub p}, included the effects of ohmic losses of the metals and changes in the dielectric properties due to the temperature dependence of (i) the intraband behavior in the Drude model and (ii) the interband critical point transition energies which involve the d-bands of Au and Ag. We show that an inclusion of both intraband and interband effects is essential when calculating the ω vs k SPP dispersion relation, plasmon density of states (DOS), and the dependence of F{sub p} on frequency and temperature. Moreover, the “back bending” in the SPP dispersion relation when including ohmic losses can cause a finite DOS above ω{sub sp} and lead to a measurable F{sub p} in a limited energy range above ω{sub sp}, which can potentially be exploited in plasmonic devices utilizing Ag and Au.« less