Far-Infrared Spectroscopy Of Folded Transverse Acoustic Phonons In 4h-Sic

The weakest mode of the infrared active folded phonons in 4H-SiC, folded transverse acoustic (FTA) mode, has been experimentally studied. The lifetime of the FTA phonons has been determined. The lifetime is 58 +/- 4 ps at room temperature and increases to 14067 ps when the temperature is decreased to 5 K. These results were obtained by the experimental study of far-infrared transmission of the SiC crystal and its theoretical simulation using an oscillator model for the dielectric function around the phonon resonance. The FTA phonon lifetime was a fitting parameter of the model when analyzing the irregular interference pattern in the transmission spectrum measured with a high resolution (0.2 cm(-1)). Oscillator strength of the FTA phonon resonance has also been determined. It is equal to (6.0 +/- 0.5) x 10(-4) and does not depend on temperature. Published under license by AIP Publishing.