of a sample with metal masks under oxidation dominant condition for 200 seconds in fig2 b 400 seconds in fig2 c and 600 seconds in fig2 d fig3 shows surface profiling diagrams of a second sample with metal masks under etching dominant condition for various durations the sample wafer includes a substrate 30 a gan film 32 and a metal mask 34 with roughened surfaces the surface profiling diagrams of a sample with metal masks under oxidation dominant condition for 200 seconds in fig3 b 400 seconds in fig3 c and 600 seconds in fig3 d fig4 shows a structure of a vertical led wafer a multi layer epitaxial structure of an exemplary n gan up led is shown on a metal substrate 70 which can be a thick copper layer in this embodiment the multi layer epitaxial structure disposed above the metal substrate 70 includes an n gan based layer 80 an mqw active layer 78 and a reflector contact layer 74 the n gan based layer 80 has a thickness of 4 microns for example the multi layer epitaxial layer may be formed by depositing a n gan portion e g n gan layer 80 above a carrier substrate not shown depositing active.