Resonance Raman spectroscopy on strain relaxed CdZnSe/ZnSe quantum wires

Cd0.35Zn0.65Se/ZnSe and Cd0.2Zn0.8Se/ZnSe quantum wells grown by molecular beam epitaxy were patterned by electron beam lithography and wet chemical etching to give quantum wires of widths down to the sub-100 nm range. The splitting between the ZnSe LO phonon of the barrier layers and the ZnSe-like LO phonon of the quantum well layer was investigated by applying different excitation wavelengths. For two wire fields with different wire sizes excitation profiles were recorded, which show features belonging to the incoming and outgoing resonance of the LO phonon fundamental vibration and its first overtone. As a result, the LO phonon wavenumber of the wire shows a small shift on changing the excitation wavelength, which is due to changes in the relative intensities of the contributions of the wire center and the wire edges. The wavenumber positions of these two peak contributions are independent of the different resonance conditions at the edge and in the middle of the wire.