Abstract: Embodiments of the invention generally relate to a method for selectively etching or otherwise removing copper or other metallic contaminants from a substrate, such as a gallium arsenide wafer. In one embodiment, a method for selectively removing metallic contaminants from a substrate surface is provided which includes exposing a substrate to a peroxide clean solution, exposing the substrate to a hydroxide clean solution, and exposing the substrate to a selective etch solution containing potassium iodide, iodine, sulfuric acid, and water during a selective etch process. The substrate generally contains gallium arsenide material, such as crystalline gallium arsenide, and is usually a growth substrate for an epitaxial lift off (ELO) process. The copper or other metallic contaminants disposed on the substrate may be selectively etched at a rate of about 500 times, about 1,000 times, about 2,000 times, or about 4,000 times or greater than the gallium arsenide material.