Single AlxGa1-xAs nanowires probed by Raman spectroscopy

The stoichiometry of single ternary III-V semiconductor nanowires was analyzed by Raman spectroscopy. Free-standing AlxGa1-xAs nanowires were obtained through metal organic vapor phase epitaxy (MOVPE) by the vapor liquid solid (VLS) mechanism on GaAs substrates. The as-grown nanowires were studied with a scanning confocal Raman spectrometer (spatial resolution approximate to 300 nm). They were located by Rayleigh imaging and individual nanowires selected for Raman spectroscopy. The acquired spectra exhibit 2-mode behavior. The stoichiometry of single nanowires was determined based on the frequencies of the GaAs- and AlAs-like transversal optical (TO) and longitudinal optical (LO) peaks with an accuracy of below 10%. Measurements at different positions along the axis revealed variations of the composition within single nanowires. This non-uniformity evidences that the nanowires possess an internal structure.