Effect of Electric Dipoles on Fermi Level Positioning at the Interface between Ultrathin Al2O3 Films and Differently Reconstructed In0.53Ga0.47As(001) Surfaces

The role played by electric dipoles at the interface Al2O3/In0.53Ga0.47As(001) has been investigated in a whole in situ approach by means of scanning tunneling microscopy/spectroscopy and X-ray photoelectron spectroscopy (XPS) in order to study local and macroscopic features, respectively. The initial pinned Fermi level (FL) shifts toward midgap after oxide deposition in both (2 x 4) and (4 x 2) reconstructions, while a reconstruction-dependent FL restoring is observed after annealing at 200 degrees C. This behavior is rationalized in terms of formation and suppression of positive charge in the as-grown oxide resulting from in situ XPS of the interface band line up.