Abstract: A method of electrochemically etching a device, including forming a semiconductor substrate having a p-type semiconductor region on an n-type semiconductor region. A discrete semiconductor region is formed on the p-type semiconductor region and is isolated from the n-type semiconductor region. The n-type semiconductor region is exposed to an electrolyte with an electrical bias applied between the n-type semiconductor region and the electrolyte. The n-type semiconductor region is also exposed to radiation having energy sufficient to excite electron-hole pairs. In addition, a p-n junction reverse bias is applied between the p-type semiconductor region and the n-type semiconductor region to prevent the p-type semiconductor region and the discrete semiconductor region from etching while portions of the n-type semiconductor region exposed to the electrolyte and the radiation are etched.