Increased range of Fermi-level stabilization energy at metal/melt-grown GaAs(100) interfaces

Abstract

We report a room temperature soft x-ray photoemission spectroscopic study of electronic barrier formation and chemistry at Al, Ag, and Au contacts with horizontal Bridgman-grown GaAs(100) surfaces, prepared by etching, heat-cleaning in situ, and As-capping. As reported previously, we observe a pronounced chemical reaction with formation of dissociated Ga for Al, a minimal interface reaction for Ag, and interdiffusion for Au. However, we find significant differences in the interface electronic barrier heights between the present metal/melt-grown GaAs(100) contacts and those made on cleaved (110) surfaces as well as on melt-grown (100) surfaces. We obtain Schottky barrier heights of 0.62, 0.85, and 1.03 eV respectively for Al, Ag, and Au/GaAs interfaces covering a range of 0.41eV - in contrast to the 0.2-0.3 eV range obtained earlier for both cleaved (110) and heat-cleaned (100) surfaces as well as the 0.7 eV range observed for metal/molecular beam epitaxy GaAs(100) interfaces. This intermediate behavior underscores the dependence of barrier height variation on different growth and interface processing techniques.