Straight and Smooth Etching of GaN (1100) Plane by Combination of Reactive Ion Etching and KOH Wet Etching Techniques

GaN striped structures along the <11 20 > and <1 100 > directions were fabricated by a combination etching technique, consisting of reactive ion etching followed by KOH wet etching. After wet etching, the sidewalls of the striped structures along the <11 20 > direction became very smooth and straight, compared with normal wet etching and dry etching. From the differences of the etching along the <1 100 > direction, it was found that etching mainly occurs in the (1 100) plane. This phenomenon can be explained by the action of OH - ions, which are repelled by N dangling bonds on the surface and which attack Ga back bonds as well as the mechanism of (000 1) polar GaN etching.