Chemistry of S/GaAs and metal/S/GaAs systems Available to Purchase

Bonding states and the band bending of S/n‐GaAs (001) and metal/S/n‐GaAs (001) systems are studied by synchrotron radiation photoemission spectroscopy (SRPES). The difference in the surface chemistry between the (NH₄)₂S_x‐treated GaAs and the sulfur‐chemisorbed GaAs is explained well by the formation of the sulfur‐rich transition layer for the (NH₄)₂S_x‐treated GaAs. A structural model for the annealed S/GaAs (001) system is proposed, in which the surface is terminated with Ga–S bonds. The barrier height of the Al, Au, and In Schottky contacts on (NH₄)₂S_x‐treated n‐GaAs is also determined to be about 0.4, 0.7, and 0.3 eV, respectively, by SRPES for the first time, which are in fairly good agreement with I–V characteristics of the metal/S/n‐GaAs Schottky diodes. It is found that the oxide‐free interface with a sulfur interlayer plays an important role for the metal‐dependent Schottky barrier formation.