Electrochemical formation and properties of n-GaAs/Au and n-GaAs/Ag Schottky barriers: Influence of surface composition upon the barrier height

Abstract

The barrier height Φ_B of electrochemically formed n-GaAs/Au Schottky barriers is investigated as a function of deposition potential V_D . Two potential regions can be distinguished: one in which Φ_B is comparable to the value of the contacts made by evaporation and another one in which Φ_B is higher. This is explained on the basis of a different surface composition of GaAs in the respective potential regions. At more positive V_D , gold will be deposited upon a surface at which the Ga atoms are –O⁻ terminated. This leads to the formation of a Au^δ+–O^δ− dipole layer at the interface and hence to an increase in Φ_B . At more negative V_D , metallic Ga will be formed during the cathodic decomposition of n-GaAs. As a consequence, surface Ga–O⁻ groups will no longer be present, no surface dipole layers will be formed and Φ_B will be lower. This interpretation is supported by results, obtained on n-GaAs/Ag Schottky barriers formed in solutions with different pH.