Coherent phonon spectroscopy of a high-quality InN epitaxial layer is carried out using time-resolved second-harmonic generation. A coherent longitudinal optical phonon and plasmon coupling mode only at 447 cm -1 can be resolved in the spectrum. Its frequency shows no dependence on the photoinjected carrier density up to 1.5 × 10 19 cm -3. This phenomenon is attributed to the hybridization of a coherent A 1(LO) phonon with the intrinsic cold plasma accumulated in the near-surface region of InN, where the plasma density could reach on the order of 10 20 cm -3, much higher than the bulk carrier concentration 1 × 10 18 cm -3 determined by Hall effect measurement.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)