Formation and Control of Hexagonal Pyramid Structures from GaN -Based Pillar-Shaped Structures Using Focused Ion-Beam Process

The formation of controllable 3D structures on the surface of layered optoelectronic devices using GaN-based semiconductors is important for improving the external quantum efficiency by enhancing the light-emitting efficiency. In this study, as-grown short hexagonal pillar structures on GaN-based semiconductors were transformed into a hexagonal pyramid shape during a focused ion-beam process. After forming the hexagonal pyramid shape, it was found that the size of the hexagonal pyramid can be adjusted by varying the sputtering time while preserving the pyramid shape. The transformation of the as-grown pillar structures to 3D hexagonal pyramids was demonstrated by analyzing the morphological evolution with the sputtering time by simulating the FIB process and calculating the effective ion bombardment area during sputtering.