RESONANT MICRO-RAMAN INVESTIGATIONS OF THE ZNSE-LO SPLITTING IN II-VISEMICONDUCTOR QUANTUM WIRES

Resonant micro-Raman spectroscopy was performed on ZnSe/Cd0.2Zn0.8Se q uantum wires. The LO phonon frequencies observed for the wires were in vestigated as a function of the temperature and the wire width. ZnSe/C d0.2Zn0.8Se quantum wells grown by molecular beam epitaxy were pattern ed by electron beam lithography and wet chemical etching to obtain qua ntum wires with widths down to the sub-100 nm region. The sample under investigation consisted of different areas each containing wires with well defined widths. Micro-Raman spectroscopy enabled us to perform m easurements on a particular area of the sample. By this method Raman s pectra could be obtained as a function of the wire width. The sample t emperature was chosen to be between room temperature and 9 K. A splitt ing of the ZnSe and the ZnSe-like LO phonons of the ZnSe/Cd0.2Zn0.8Se quantum wires was observed. The size of this splitting was found to de pend only on the wire width and not on the temperature. This behavior is due to the strain relaxation, which occurs at the edge zone of each quantum wire. The increasing influence of the edge zone for decreasin g wire width is the reason for the wire width dependence of the splitt ing between the ZnSe and the ZnSe-like LO phonon. As a result, the imp ortance of partial strain relaxation for the discussion of the vibroni c properties of the patterned semiconductor systems was confirmed. (C) 1997 American Institute of Physics.