Wafer-level fabrication of nanoscale patterned sapphire substrates with broadband optical transmittance

This paper presents wafer-level aperiodic nanostructures fabrication of sapphire substrates with broadband optical transmittance. The nanostructures were patterned by using nickel silicide as a hard mask, and performed by inductively coupled plasma reactive ion etching. The sapphire substrates with nanostructures exhibit high transmittance at wide incident angles over broadband spectra compared with conventional sapphire substrates. The transmittance of visible to near-IR spectra was found to be 94%. In the mid-IR spectrum, the transmittance exceeds 88% until the reflection is no longer suppressed by nanostructures. The polarization properties show the nanostructure enhances the reflectivity ratio by at least 50%.