Experimental extract and experienced formulas of refractive indices of GaAs and AlAs at high temperature by high resolution x-ray diffraction and optical reflectivity measurement

Abstract

Distributed Bragg reflector (DBR) structure has been widely used in optoelectronic devices during the MBE growth. Precisely controlling the growth thickness of superlattice layers is very important for successfully achieving the optical properties of DBR structure. In general, an ideal thickness controlling with better than 1% accuracy is needed to realize the devices. Both methods of optical reflection difference and dynamic optical reflectivity are usually used to measure the growth rate of epitaxial growth layer in MBE experiment. During the calculation of the growth rate, however, the refractive index at high temperature is needed. The refractive indices of semiconductor materials axe the sensitive parameters to the temperature and the wavelength of incident laser. Up to now, there are not enough parameters for the semiconductor material indices at high temperature during a relatively wide wavelength region. In this paper, we use high resolution x-ray diffraction (HRXRD) technique to decide the superlattice thickness. With these data, we calculate and extract the refractive indices of the epitaxial layers of GaAs and AlAs. The accuracy of extracted indices is certified by optical reflectivity spectrum.