An electrolytic etching technique has been developed which can remove p‐type GaAs substrates from thin (2–10µ) n‐type layers of or . Sodium hydroxide is used as the electrolyte, and is sprayed continually over the etching surface to prevent the build‐up of “flakes” on the p‐type surface as by‐products of the etching process. Such flakes serve as an effective mask to the etching process and, unless removed, result in irregular or matte surfaces on the n‐type layer after removal of the p‐type material. The removal of these flakes by the spray of leads to shiny, unblemished n‐type surfaces over large‐area wafers (2–5 cm2∥. The extension of this electrolytic etching technique to thin, vapor‐grown layers has applications in electron microscopy, luminescence and optical measurements, and in semiconductor device fabrication.