Coherent optical phonon generation in HVPE grown, 150 micron thick GaN by the impulsive stimulated Raman scattering

Summary form only given. Since the advent of ultrashort pulse lasers, the excitation and the detection of coherent lattice vibrations have attracted much interests.GaN is now one of the hottest materials for its enormous potential in device applications. Large acoustic lattice vibrations in GaN/InGaN multiple quantum wells were demonstrated by Sun et al. However coherent optical phonon oscillations have not been demonstrated yet for GaN. In this paper, we report the first observation of coherent optical phonon oscillations in GaN. Using time-resolved REOS technique with 15 fs, 800 nm pulses, we observe two E2 modes with frequencies of 4.304 THz and 17.03 THz and one Al mode with frequency of 22.0 THz. By the HVPE (hydride vapor phase epitaxy) method, 150 /spl mu/m thick GaN with wurtzite structure was grown along the c-axis.