| Summary: | 碩士 === 國立清華大學 === 電子工程研究所 === 94 === Abstract
GaN based light-emitting diodes (LEDs) have become the most popular material for UV to green light LEDs. Because it has high band gap characteristics and wavelength variation by changing the concentration of Al, Ga and In. Solid-state LEDs with high extraction efficiency are currently in great demand for various applications including full color flat displays, automotive interior and exterior lights, and general lighting. However, while the internal quantum efficiency of visible LEDs is close to 100%, most of the light is lost due to total internal reflection (TIR).
In order to enhance the extraction efficiency of GaN based LEDs, we separately fabricated GaN photonic crystal LEDs with anodic aluminum oxide (AAO) template and e-beam lithography technologies. According to our simulation result, we find out the optimum design of 2D photonic crystal GaN LEDs, and fabricate them according to this result. Hexagonal lattice PCs with diameter/periodicity of 300/500 nm were patterned by etching. Electronics measurement system and micro PL system are used to analyze the electrical and optical properties of PC LED. We observed that the enhancement of efficiency of PC LED is obvious higher than that of the as-grown LED. And we find that the forward voltage of LEDs which were fabricated with the AAO template and e-beam lithography technologies is lower than that of the as-grown LED. In addition we studied the optical properties of PC LED, and we observed the photo luminescence (PL) intensity of PC LED is enhanced four-fold relative to that of the as-grown LED, and there are not obvious shift of the peak wavelength.
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