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Title: Deep-level emission in ZnO nanowires and bulk crystals: Excitation-intensity dependence versus crystalline quality

The excitation-intensity dependence of the excitonic near-band-edge emission (NBE) and deep-level related emission (DLE) bands in ZnO nanowires and bulk crystals is studied, which show distinctly different power laws. The behavior can be well explained with a rate-equation model taking into account deep donor and acceptor levels with certain capture cross sections for electrons from the conduction band and different radiative lifetimes. In addition, a further crucial ingredient of this model is the background n-type doping concentration inherent in almost all ZnO single crystals. The interplay of the deep defects and the background free-electron concentration in the conduction band at room temperature reproduces the experimental results well over a wide range of excitation intensities (almost five orders of magnitude). The results demonstrate that for many ZnO bulk samples and nanostructures, the relative intensity R = I{sub NBE}/I{sub DLE} can be adjusted over a wide range by varying the excitation intensity, thus, showing that R should not be taken as an indicator for the crystalline quality of ZnO samples unless absolute photoluminescence intensities under calibrated excitation conditions are compared. On the other hand, the results establish an all-optical technique to determine the relative doping levels in different ZnO samples by measuring the excitation-intensitymore » dependence of the UV and visible luminescence bands.« less
Authors:
;  [1] ;  [2] ; ;  [3]
  1. Institute of Solid State Physics, University of Bremen, Bremen (Germany)
  2. Institute of Solid State Physics, University of Jena, Jena (Germany)
  3. Institute of Microsystems Engineering, IMTEK, University of Freiburg, Freiburg (Germany)
Publication Date:
OSTI Identifier:
22303996
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 23; 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; 77 NANOSCIENCE AND NANOTECHNOLOGY; CAPTURE; CONCENTRATION RATIO; CROSS SECTIONS; DEFECTS; ELECTRONS; EXCITATION; LIFETIME; MONOCRYSTALS; NANOWIRES; PHOTOLUMINESCENCE; QUANTUM WIRES; REACTION KINETICS; TEMPERATURE RANGE 0273-0400 K; ZINC OXIDES