Metal/GaAs interface chemical and electronic properties: GaAs orientation dependence

Abstract

Synchrotron radiation photoemission results for metals on intentionally misoriented molecular-beam epitaxy GaAs(100) surfaces reveal an orientation-dependent interfacial chemistry and Schottky barrier heights at low temperature (90 K). Previous measurements for different metals on aligned GaAs(100) surfaces show a Fermi stabilization energy range of 0.95 eV. However, for Au and Al on 2° misoriented specimens, narrower ranges are observed: 0.65 eV for GaAs surfaces cut towards [110] and 0.45 eV for surfaces cut towards [111] with either Ga or As dangling bonds perpendicular to the step edges. The decrease in the range of the Fermi level stabilization energies is mainly due to the increase in Schottky barrier heights for Al contacts on misoriented specimens, where a more pronounced interface reaction is observed. Our results indicate that the observed degree of chemical reaction and diffusion increases in the order of GaAs(100) surfaces tilted toward [110], [111]A, and [111]B. Our bonding results emphasize the importance of interfacial chemistry and the perfection of the substrate GaAs in the metal/GaAs junction electronic properties.