Metal electrode influence on the wet selective etching of GaAs/AlGaAs

Metal electrodes were found to influence the wet selective etching of GaAs in a citric acid/hydrogen peroxide solution. The authors found that metal films such as a Cr/Au or Ti/Au alloy deposited on a semiconductor surface can mostly prevent the etching of GaAs. The GaAs sacrificial material that was exposed to the selective etchant near the metal electrode was not removed at all. Contrast experiments show that it can be removed selectively if no metal is present on the surface or if the GaAs is located far enough from the metal. Electrochemical analyses were undertaken to determine the passivation mechanism.