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

Journal Article · Sat Jun 21 04:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4884611· OSTI ID:22303996

Hou, Dongchao; Voss, Tobias ^[1]; Ronning, Carsten ^[2]; Menzel, Andreas; Zacharias, Margit ^[3]

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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)

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-intensity dependence of the UV and visible luminescence bands.

• OSTI ID: 22303996
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 23 Vol. 115; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

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