Due to lack of suitable lattice matched substrates, III-Nitride materials are usually grown on sapphire, SiC, and silicon. The heteroepitaxy of GaN on these substrates often incorporates a high density of dislocation and point defects due to lattice and thermal mismatch. It is desirable to reduce the defect density in III-Nitrides in order to fabricate longer lifetime and high brightness light emitting diodes, lasers, and high-electron mobility transistors. In this context, nano-scale epitaxy on patterned Si substrates allows lateral growth, which eventually leads to a reduction of defect density and strain in the overgrown GaN films. Large area nano-patterning with dielectric masks would also be useful to fabricate highly-ordered and dense nitride nanostructures by selective area homo- and hetero-epitaxy.