ELECTRO-OPTICAL INVESTIGATION OF THE POTENTIAL DROP AT III/V SEMICONDUCTOR ELECTROLYTE INTERFACES

The semiconductor/electrolyte junction is investigated for n-type InP, GaAs, and Ga//0//. //4//7In//0//. //5//3As in contact with aqueous an nonaqueous electroytes. Electrolyte electroreflectance is used as an in situ probe for determining the distribution of potential and energy states at the interface. We find that the interface states at InP and GaAs electrodes have a density of 2 multiplied by 10**1**2 cm** minus **2 eV** minus **1 and 3-10 multiplied by 10**1**2 cm** minus **2 eV** minus **1, respectively, and that this density is pH independent for InP (semiconductor controlled) whereas for GaAs it is pH dependent (solvent controlled). For Ga//0//. //4//7In//0//. //5//3As, the situation more complex, and interfaces clean from energy states (density lower than 10**1**2 cm** minus **2 eV** minus **1) can be obtained at pH 0 as well as a complete Fermi level pinning (density approx. 10**1**5 cm** minus **2 eV** minus **1) depending on the bias.