Gallium nitride light emitter on a patterned sapphire substrate for improved defectivity and light extraction efficiency

Gallium nitride light emitting diodes were deposited on a sapphire substrate that was pre-patterned with an ordered two-dimensional structure. The size and arrangement of the substrate surface pattern was designed to increase the diffraction and extraction of light from the device as well as define the grain size and thus dislocation density of the GaN crystal. A close-packing of self-assembled SiO2 nanospheres was used as the sacrificial etch mask. The etch process transferred a two-dimensional pattern into the sapphire substrate with a peak-to-peak dimension of approximately 250 nm. The distance was selected to match the emission wavelength in the crystal for optimal light scattering. Additionally, the dimensions of the crystal artificially defined the grain size of the GaN in contrast to the kinetically controlled grain size in a standard GaN on sapphire growth process.