CHARACTERIZATION OF SOME TERNARY III-V SEMICONDUCTOR ELECTROLYTE INTERFACES UTILIZING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

Single crystal GaInP2 and Ga1-xAlxAs-aqueous electrolyte interfaces were investigated utilizing electrochemical impedance spectroscopy. Both materials have band gaps that are much larger than the theoretical free energy required to decompose water (1.23 eV) and may do so depending on the energetic positions of the band edges. Impedance spectra (500 muHz-100 kHz) were used to model the interface in terms of a space-charge layer capacitance, a constant phase element and oxide film capacitance in some cases, and associated resistances. The flat-band potential and carrier concentrations were determined from Mott-Schottky plots. It was found that the corresponding band edges of both materials fall short of encompassing both the hydrogen and oxygen redox levels and are thus not capable of splitting water in the absence of an external bias.