Refractive indices of MBE-grown Al_{x}Ga_{(1-x)}As ternary alloys in the transparent wavelength regi

A series of AlxGa(1-x)As ternary alloys were grown by molecular beam epitaxy (MBE) at the technologically relevant composition range, x < 0.45, and characterized using spectroscopic ellipsometry to provide accurate refractive index values in the wavelength region below the bandgap. Particular attention is given to O-band and C-band telecommunication wavelengths around 1.3 μm and 1.55 μm, as well as at 825 nm. MBE gave a very high accuracy for grown layer thicknesses, and the alloys’ precise compositions and bandgap values were confirmed using high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL), to improve the refractive index model fitting accuracy. This work is the first systematic study for MBE-grown AlxGa(1-x)As across a wide spectral range. In addition, we employed a very rigorous measurement-fitting procedure which we present in detail.