Raman spectroscopy of epitaxial InGaN/Si in the central composition range.

InGaN alloys are of raising interest for many applications. The possibility of tuning their functional properties with the composition sets the importance of finding methods to characterize these materials in a fast and non-destructive way. Raman spectroscopy is one of these techniques, being able to yield information about the composition, strain, and other relevant parameters. However, the method of measuring the composition with a calibration of the maximum A₁(LO) band is today limited to regions which are either rich in In or in Ga. The middle composition range still needs a calibration. By measuring the Raman spectra of different In_xGa_1-xN alloys grown epitaxially on Si and by comparing them with the results from X-ray diffraction, we investigated this missing region of compositions. Within the range of 30%–65%, we have found that the position of the maximum of A₁(LO) scales with the In fraction x as ω_x = 736 – 135x – 24x² cm⁻¹. With this calibration, it is possible to determine, by Raman spectroscopy, the composition of an unknown alloy with an uncertainty of 5%. [ABSTRACT FROM AUTHOR]