Dynamic optical reflectivity to monitor the real-time metalorganic molecular beam epitaxial growth of AlGaAs layers

Abstract

Oscillations in the reflectivity of Al x Ga1−x As, grown on GaAs at 870 K have been measured at 632.8 nm over the range 0≤x≤1. The oscillations are fitted to the standard theory of reflection from a bilayer with the complex refractive index (n+ik) of substrate and film as fitting parameters. For GaAs the values of n and k are measured as 3.9+i0.23 at 870 K. Assuming n varies linearly with x for Al x Ga1−x As between 3.1(A1As) and 3.9(GaAs) then the period of the oscillations gives an accurate measurement of growth rate, while the amplitude allows the film composition to be monitored simultaneously. All layers were grown by metalorganic molecular beam epitaxy (MOMBE).