A workpiece is implanted to a first depth to form a first amorphized region. This amorphized region is then etched to the first depth. After etching, the workpiece is implanted to a second depth to form a second amorphized region below a location of the first amorphized region. The second amorphized region is then etched to the second depth. The implant and etch steps may be repeated until structure is formed to the desired depth. The workpiece may be, for example, a compound semiconductor, such as GaN, a magnetic material, silicon, or other materials.