Long-Lived, Coherent Acoustic Phonon Oscillations in GaN Single Crystals
We report on coherent acoustic phonon (CAP) oscillations studied in high-quality bulk GaN single crystals with a two-color femtosecond optical pump-probe technique. Using a far-above-the-band gap ultraviolet excitation (~270 nm wavelength) and a near-infrared probe beam (~810 nm wavelength), the long-lived, CAP transients were observed within a 10 ns time-delay window between the pump and probe pulses, with a dispersionless (proportional to the probe-beam wave vector) frequency of ~45 GHz. The measured CAP attenuation corresponded directly to the absorption of the probe light in bulk GaN, indicating that the actual (intrinsic) phonon-wave attenuation in our crystals was significantly smaller than the measured 65.8 cm^-1 value. The velocity of the phonon propagation was equal to the velocity of sound in GaN.
- Research Organization:
- Laboratory for Laser Energetics, University of Rochester, Rochester, NY
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC52-92SF19460
- OSTI ID:
- 875444
- Report Number(s):
- DOE/SF/19460-649; APPLAB; 1608; 2005-140; TRN: US0703305
- Journal Information:
- Applied Physics Letters, Vol. 88; ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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