POLARIZED RAMAN AND PHOTOLUMINESCENCE STUDY ON SILICON QUANTUM WIRES

A detailed Raman and photoluminescence study was performed on Si quant um wires fabricated on crystalline silicon (100). A shift of the phono n frequency was observed indicative of a compressive stress of about 9 .5 kbar, possibly originating from the oxide skin grown on the wire su rface by high temperature thermal oxidation. A splitting of the Raman phonon was also observed and interpreted as originating from the exist ing stress and/or from the excitation of phonons polarized parallel an d normal to the direction of confinement. The photoluminescence emissi on was found to depend on the excitation wavelength and on the polariz ation of the laser beam. The energy and efficiency of the emitted lumi nescence increased with decreasing laser wavelength. This was interpre ted as an effect due to the size distribution of the studied wires, si nce thin wires with a higher band gap than thick wires can be excited by shorter laser wavelengths. The photoluminescence efficiency was sig nificantly higher when the laser beam was polarized in the direction o f confinement in agreement with theoretical predictions. The emitted l uminescence was also polarized preferentially in the direction of conf inement. This resulted in depolarization of the emitted light when the laser beam was polarized along the wire axis, normal to the direction of confinement. (C) 1998 American Institute of Physics. [S0021-8979(9 8)06114-3].