| Etch rate of polycrystalline AlN in 45wt% KOH as function of time, at 60 °C. |
| Sample A before (a) and after (b,c,d) etching. (a) before etching; (b) after etching; (c) enlarged image of circle in (a) after etching; and (d) enlarged image of circle in (b) after etching |
| Crystal produced by microwave, after 10 minute etching |
| AlN crystal grown on SiC substrate for 10 minute etching. (a) before etching; and (b) after etching |