Lin Y.-S.,National Tsing Hua University |
Hsu W.-C.,Sino American Silicon Products Incorporation |
Huang K.-C.,Instrument Technology Research Center |
Yeh J.A.,National Tsing Hua University |
Yeh J.A.,Instrument Technology Research Center
Applied Surface Science | Year: 2011
The wafer-level aperiodic nanostructures were fabricated atop the sapphire substrates in order to increase the transmittance over broadband spectra. The fabrication was presented along with characterization of their optical properties. The nanostructures were patterned using natural lithography with nickel silicide as a hard mask, and the subsequent etching was performed using inductively coupled plasma dry-etching method. The sapphire substrates with nanostructures compared to conventional sapphire substrates, which exhibit antireflective characteristics over broadband spectra at a wide range of incident angles. The nanostructures reduce the reflection down to 5% in the visible spectrum for normal incidence. The transmittance of visible to near-IR spectra was found to be 94% at normal incidence and over 90% at an incident angle of 45°. In the mid-IR spectrum, the transmittance exceeds 88% until the reflection is no longer suppressed by nanostructures. The polarization properties have also been investigated. The nanostructures can enhance the reflectivity ratio 90% for wavelengths shorter than 400 nm. As the amplitude ratio, enhanced from 50% to 80% over the whole visible spectrum. © 2011 Elsevier B.V. All rights reserved.
Lin B.-W.,National Chiao Tung University |
Chang C.-C.,Sino American Silicon Products Incorporation |
Hsieh C.-Y.,Sino American Silicon Products Incorporation |
Wang B.-M.,Sino American Silicon Products Incorporation |
And 2 more authors.
IEEE Photonics Technology Letters | Year: 2011
Periodic tent-like post patterns on a-plane sapphire substrates were fabricated using a two-step etching process. They were denoted as a-plane dot pattern sapphire substrate (ADPSS). Compared with the GaN-based light-emitting diode (LED) grown on a-plane sapphire without any pattern (AFlat), the ADPSS-LED has higher output power, light extraction efficiency (LEE), and external quantum efficiency (EQE), and better crystal quality. The output power of ADPSS-LED was 9.6 mW, which was 68.4% larger than the AFlat-LED. In addition, the blue shift of ADPSS-LED was found to be less than that of AFlat-LED. © 2006 IEEE.