Anisotropic reflectance from semiconductor surfaces for in-situ monitoring in epitaxial growth systems

Spectroscopy of the anisotropic part of the reflectance (reflectance anisotropy spectroscopy: RAS or reflectance difference spectroscopy: RDS) is a promising diagnostic technique for real-time studies of semiconductor surfaces during epitaxial growth. This in-situ technique turns out to be highly sensitive to the status of the surface and, moreover, requires only slight modifications to standard epitaxial growth systems. In this paper, RAS studies of semiconductor epitaxial growth are reviewed and state-of-the-art results are reported. Primarily, spectra from III-V semiconductors are discussed in terms of surface bonds and surface reconstructions. Time-resolved measurements allow to study the dynamics of surface processes such as exchange reactions which are important for the optimisation of heterointerfaces. Furthermore, the oscillatory behaviour of the island growth mode shows up in the RAS signal and can be utilized for growth rate monitoring and in-situ measurement of composition. The combination of these features allows, for example, the control of the growth of a superlattice on a submonolayer scale.