Photodissolution Kinetics of n ‐ GaAs in 1M KOH and Calculation of the Stabilization by Se2−: Effect of the Ru3+ Surface Treatment

Abstract

We present a method for obtaining the photodissolution kinetics of in . It is based upon the simultaneous measurement of photocurrent and impedance. It is shown that an accurate determination of the band bending is absolutely necessary to obtain the actual kinetic constants. In fact, the semiconductor bandedges shift toward positive potentials when illumination is increased. In addition, a potential‐dependent surface charge variation is responsible for another voltage drop in the Helmholtz layer which modifies the band bending. This is shown by the surface‐state capacitance, which presents sharp variations in applied potential. According to the current expression, , a value of is found to be independent of the photon flux, the surface orientation, and the ruthenium treatment. This value is used to estimate the stabilization coefficient of the junction. A value of close to 100% is found. We then discuss the ruthenium treatment in selenide solution, where energetic conditions for charge transfer are changed through surface‐charge modifications. Our calculations show an improvement of both cell performances and stability, as expected, when the electrode is Ru treated. Moreover, the effect of Ru3+ cations upon the impedance data suggests that the flatband potential shift is linked to chemical surface modifications, prior to corrosion. This is confirmed by the fact that is not photon‐flux dependent. Finally, we examine whether the bonds with one electron might be responsible for the bandedge shift and the behavior of the junction. The case of the Se2− stabilized junction is also discussed.