In situ optical monitoring of the interface strain relaxation of InGaAs/GaAs grown by molecular‐beam epitaxy

Abstract

The evolution of the surface morphology during the MBE growth of InxGa1−xAs on GaAs (001) is studied by in situ Reflectance-difference (RD) spectroscopy and reflection high-energy electron diffraction (RHEED). InxGa1−xAs layers with x = 0.3 nominal compositions were growth under different arsenic overpressures. For arsenic-rich conditions RHEED measurements show that the growth mode is largely two-dimensional (2D). In contrast, under As-deficient conditions a 2D-3D growth morphology transition is observed upon closing the In and Ga shutters. Concurrently with this transition, the RD intensity at 2.5 eV shows a sharp increase, indicating the formation of anisotropic InxGa1−xAs islands. We further show that low growth rates (0.3 ML/s) result in higher RD amplitudes and thus in InGaAs islands with enhanced anisotropy.