Kinetic Investigation on the Photoetching Reaction of n-Type GaAs by Scanning Electrochemical Microscopy

The physicochemical principle of photocorrosion and photoetching is the internal photoelectric effect of semiconductors. However, the kinetic investigation of interfacial charge transfer induced by this phenomenon has been seldom reported due to its microdomain bipolarity. GaAs is a direct band gap semiconductor with high saturated electron velocity and high electron mobility. Once the photogenerated electrons on a n-type GaAs surface are removed by Fe3+ in the solution, it will dissolve due to the residual positive holes; i.e., the photoetching process will occur. By employing scanning electrochemical microscopy (SECM), the photoetching rates of n-type GaAs are obtained about similar to 10(-4) mol.m(-2) s(-1) with Fe3+ cation as electron acceptor. The rate-determining step (rds) is proved as the charge separation process at low illuminating intensity, and the mass transfer of Fe3+ in the solution at high illuminating intensity. Moreover, the photoetching process is developed as a controllable micromachining method for semiconductor materials.