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.

GaN-based striped structures were fabricated using Al 0.2 Ga 0.8 N/GaN single heterostructure by combination of dry/wet etching with taking into account GaN crystal structure. After following wet-etching, the sidewalls of striped structures along the <11 2 0> direction became very smooth and straight compared with that of as dry-etched. We estimated mobility of electron in field effect transistors (FETs) consists striped structures along the <11 2 0> direction from I-V characteristics. The mobility of the as dry-etched striped structures was drastically reduced from the not-patterned Al 0.2 Ga 0.8 N/GaN single heterostructure. In contrast, the mobility of the smooth striped structure FETs were effectively recovered to that of the notpatterned one. These results suggest that following KOH wet-etching can remove the damaged/rough layer indued by the RIE dry-etching.