Selective defect blocking by self-assembled silica nanospheres for high quality GaN template

We demonstrate the use of self-assembled silica nanospheres as a mask to block the propagation of threading dislocations on a defect selective etched GaN template. The selective etched pits were generated on the latent dislocations of GaN template using the wet etching technique. The silica nanospheres (500 nm) were then coated on the selective etched GaN using a spin-coating method. The silica nanospheres were confined in the etched pits by capillary force and geometric shape. The GaN template was then regrown by epitaxial overgrowth using metallorganic chemical vapor deposition. As a result, the regrown GaN layer was significantly reduced from 5 × 10⁹ to 3 × 10⁷ cm^-2 in threading dislocation density and from 3 × 10 ⁷ to 3 × 10⁵ cm^-2 in etched pit density. These significant enhancements are attributable to selective defect blocking by self-assembled silica nanospheres.