Journal article
Carrier dynamics in bulk ZnO. II. Transient photoconductivity measured by time-resolved terahertz spectroscopy
Physical review. B, v 80(23)
01 Dec 2009
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Abstract
We employ time-resolved terahertz spectroscopy to investigate the dynamics of photogenerated electrons and holes in bulk ZnO at temperatures below 100 K. Carrier density and mobility are extracted by fitting the Drude model to the measured frequency-dependent complex photoconductivity. Electrons are excited with below-band-gap photons (387, 400, or 775 nm) to states well above the conduction-band minimum by one-photon absorption from midgap states. Two-photon absorption also occurs with blue excitation, leading to the generation of mobile valence-band holes as well as electrons. Within a few picoseconds of excitation with blue photons, carriers have ambipolar scattering times of over 500 fs, corresponding to combined carrier mobility of similar to 3500 cm(2) V-1 s(-1). Scattering times decrease to similar to 300 fs as the light holes relax to the heavy-hole bands over the next tens to hundreds of picoseconds. Higher temperatures and higher excitation fluences result in faster relaxation, as well as faster recombination, due to increased carrier interaction with phonons and other carriers. Carrier lifetimes at low excitation fluences with blue photons range from 20 ps at 80 K to nearly 200 ps below 40 K. Conversely, photoexcitation with red photons produces dynamics that are independent of fluence, which is likely due the lack of mobile holes compared to blue excitation.
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Details
- Title
- Carrier dynamics in bulk ZnO. II. Transient photoconductivity measured by time-resolved terahertz spectroscopy
- Creators
- Jason B. Baxter - Drexel UniversityCharles A. Schmuttenmaer - Yale University
- Publication Details
- Physical review. B, v 80(23)
- Publisher
- Amer Physical Soc
- Number of pages
- 10
- Grant note
- American Chemical Society Petroleum Research Fund; American Chemical Society CHE-0616875 / National Science Foundation; National Science Foundation (NSF)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Chemical and Biological Engineering
- Web of Science ID
- WOS:000273228800059
- Other Identifier
- 991019169681704721
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InCites Highlights
Data related to this publication, from InCites Benchmarking & Analytics tool:
- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Materials Science, Multidisciplinary
- Physics, Applied
- Physics, Condensed Matter