Aqueous H202 solutions are widely used for etching III-V semiconductor materials in device technology. Extensive electrochemical research has been performed to understand the mechanism of H202 as a chemical or electroless photoetchant by several groups, among which the former group of the applicant's research supervisor (Kelly) at Philips Research. The cathodic reduction of H202 at GaAs has been studied by the research group of the applicant. Persistent current oscillations have been observed which can be understood on the basis of a kinetic model proposed for the interactions of H202 with GaAs and an anomalous band-bending behavior.
The project aims to detect the reaction intermediates of the reaction o H202 at GaAs and to measure the band bending by a non-electrochemical methods. In-situ infrared spectroscopy at the electrochemical interface will be used. When applying a small potential modulation, the resulting, variation of band bending, is unambiguously accessible through a measurement of the electromodulated infrared absorption from free carriers. Such measurements, performed for various values of the applied potential, will provide a determination of the band bending, as a function of electrode potential and enable the measurement (in real time) of variations of the band bending, during, electrochemical oscillations. Furthermore, surface infrared vibrational absorption will be investigated, with special attention to AsH and GaH stretching, modes. Since the response time of hydrogen adsorption to a modulation of potential is not known, this search will be done using, modulated spectroscopy, but also differential spectroscopy, which is advantageous in the case Of slow-response species.