The authors report on the growth of GaN on AlGaN/(111)Si micropillar array by metal-organic chemical vapor
deposition. Using the substrates with micropillar array, 2 μm-thick GaN films without cracks can be achieved.
Transmission electron microscopy, atomic force microscopy, and micro-Raman studies indicate that the dislocation
density and residual stress of the GaN grown on micropillar array are also reduced. The results reveal the potential of this
type of substrates for growing GaN-based devices as well as preparing GaN freestanding substrates.
In this study, we design and fabricate a hollow optical waveguide with omni-directional reflectors in silicon-based materials. A groove is etched by inductive coupled plasma (ICP) with photolithographic process on (100) silicon wafer. The width of the groove is varied from 3.5 to 5.5 micrometer for different waveguide designs. The depth of the groove is 1.2 micrometers. Plasma enhanced chemical vapor deposition is used to deposit six pairs of Si/SiO2(0.111/0.258micrometers) on the samples. Finally, the top of the sample is covered by another silicon substrate on which the identical omni-directional reflector has been also deposited. By wafer bonding technology, the top omni-directional reflector can be combined with the groove to form a hollow optical waveguide. Light with the wavelength at 1.55 micrometers can be confined by the omni-directional reflectors at single mode operation. Polarization independent hollow optical waveguides can be achieved with this fabrication process.