Formation and optimization of undercut-microholes in InGaN light emitting diodes by using wet chemical etching

We report on the formation and optimization of undercut-microholes (UM) generated by a wet etching process. GaN epilayers with 6 μm and 15 μm polygonal holes (PH) were grown by using selective metal organic chemical vapor deposition under identical growth conditions. The samples were wet etched with either a KOH solution or a mixed H3PO4:H2SO4 solution. Both kinds of etching solution produced the formation of UM. In the case of the etching produced with the mixed H3PO4:H2SO4 solution, the angle of UM was varied with an increase of H2SO4 in the solution. The etching produced by the KOH solution was very simple, and it formed a clear UM with an angle of 62°. This was achieved without etching the hard mask because of the selective etching and crystallographic characteristics of the GaN. UM were optimized through etching with PH structures, and the results showed formation of clear UM in a 15 μm PH structure.

► The Optimization of Fabrication of Undercut-microholes structures.
► Wet etch characteristics study of GaN epilayer with etching solutions.
► The light output power improvement of GaN-light-emitting diode with Undercut-microholes.