Modification of the Fermi-level pinning of GaAs surfaces through InAs quantum dots

Room-temperature photoreflectance in van Hoof structures together with atomic force microscopy has been used to determine the influence of InAs quantum dots on the Fermi-level pinning of $\{100\}$ GaAs surfaces. We show that quantum dots with base lengths of 10 and 25 nm lead to the Fermi level being pinned approximately 250 meV deeper in the band gap, an effect which is reversible by either overgrowing the dots with GaAs or by selectively etching away the dots. These results are discussed within the framework of recent theoretical investigations of surface states due to polar facets associated with quantum dots.