| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 96 === Recently, wide-bandgap semiconductors have been attracting great interest for applications to optoelectronic devices such as light-emitting diodes (LEDs), for last few years, InGaN/GaN-based blue light-emitting diodes (LEDs) have been successfully fabricated and following comes the epochal of white light LED. However, for future illumination applications, it is very important topic to further enhance the external quantum efficiency of LED.
In this research, sapphire removal and patterned sapphire substrates (PSS) were fabricated utilizing wet chemical etching technology. A 3H2SO4：1H3PO4 volume mixture was used as the etchant to etch the sapphire substrates with 280 °C, and we obtain three different kinds of PSS LED. The experiment results indicate that 1.3 micron cylinder PSS LED has 49 % efficiency enhancement than conventional LED at 20 mA injection current.
In order to fabricate vertical-electrode LED, unlike the common technology, laser lift-off, we tried the commutative etching method to do the sapphire removal experiments employing 5H2SO4：1H3PO4 and 2H2SO4：1H3PO4 as the etchant. The etching rate ratio (RSapphire / Ru-GaN) is achieved 15. We may fabricate vertical-electrode LED utilizing the commutative etching method to remove the sapphire substrates in the future.
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