Triangular Extended Microtunnels in GaN Prepared by Selective Crystallographic Wet Chemical Etching

Extended microtunnels with triangular cross sections in thick GaN films were demonstrated using wet chemical etching on specially designed epitaxial lateral overgrowth structures. For tunnels along the and directions of GaN, the {1122} and {1011} facets are the etch stop planes with activation energies of 23 kcal/mol determined by wet chemical etching. The axial etching rate of the tunnels in the (1100) direction is twice as large than that along the (1120) direction. The highest etching rate of the tunnels in the axial direction is 1000 μm/h.