[Granted] A workpiece is implanted to improve growth of a compound semiconductor, such as GaN. This workpiece may be implanted such that the workpiece has a dose at a center different from a dose at a periphery. This workpiece also may be implanted one or more times to form a pattern of lines, which may be a grid, a series of circles, or other shapes. The distance between certain pairs of lines may be different across the workpiece.