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Proceedings Paper

Intensity-dependent dynamics of photoexcited carriers in ZnO epilayers studied using pump-probe reflectance
Author(s): Bing Guo; Y. H. Li; H. Ye; Peifu Gu; Kam Sing Wong
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Paper Abstract

The dynamics of carriers/excitons in as grown and annealed ZnO epilayers at room-temperature under high excitation densities were monitored by pump-probe(4.65/3.1 eV) differential reflectance transients on a time scale equal to 100 ps. The ΔR buildup showed a density-independent time delay of about 1.45 ps relative to the pump pulse, indicative of hot phonon effects, i.e., LO-phonon bottleneck, common to the as grown and annealed ZnO epilayers. Both appeared an initial fast ΔR decay with a time constant of about 20-25 ps due to rapid defect trapping. After the fast decay, the ΔR transient of the as grown ZnO became of sign reversal and turned to an induced absorption signal from defect levels with a decay time of several hundred picoseconds weakly dependent on excitation intensities. For the annealed ZnO, no change over in sign was observed on the slowly recovering component of ΔR, of which, in particular, the decay time was found to linearly depend upon carrier density. This finding, as confirmed by photoluminescence measurements, was attributed to a bimolecular recombination in terms of an exciton-exciton scattering in ZnO. These observations suggest that this unique pump-probe technique can provide a useful tool for understanding the defect physics of semiconducting materials.

Paper Details

Date Published: 20 January 2005
PDF: 10 pages
Proc. SPIE 5628, Semiconductor Lasers and Applications II, (20 January 2005); doi: 10.1117/12.576597
Show Author Affiliations
Bing Guo, Zhejiang Univ. (China)
Y. H. Li, Zhejiang Univ. (China)
H. Ye, Zhejiang Univ. (China)
Peifu Gu, Zhejiang Univ. (China)
Kam Sing Wong, Hong Kong Univ. of Science and Technology (Hong Kong China)

Published in SPIE Proceedings Vol. 5628:
Semiconductor Lasers and Applications II
Jian-quan Yao; Yung Jui Chen; Seok Lee, Editor(s)

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