Polarized Raman scattering of impurity modes in beryllium-doped cubic boron nitride single crystals

Impurity-induced modes at 212 and 535 cm(-1) have been studied by using Raman scattering spectroscopy in Be-doped cubic boron nitride single crystals, which have been grown by the temperature-gradient method under high pressure. Those bands show prominent polarization properties of T-2 and A(1) modes for the 212 and 535 cm(-1) bands, respectively. Based on the polarization properties and a simple calculation of a molecular model, the origin of the bands is explained by postulating resonance modes of substitutional Be with a weak force constant between the host atoms and the Be. Anomalies of a forbidden transverse optical mode and the T-2 mode due to phonon-plasma coupling caused by photoexcited free carriers have been also observed in high excitation density. (C) 2003 American Institute of Physics.