| Summary: | 碩士 === 國立臺南大學 === 光電工程研究所 === 98 === High-performance AlGaInP-based light emitting diodes (LEDs) were widely used, although the AlGaInP-based material has been developed for many years and its internal quantum efficiency has approached above 90%. However, the external quantum efficiency of AlGaInP is still low due to the optical properties limitation. A surface-roughing technique, employed by nanoimprint lithography, was studied for the light extraction efficiency of the AlGaInP light emitting diodes (LEDs). The roughing technique used in this dissertation had been effectively reduced the total internal reflection in the LED structure.
We have demonstrated improved light extraction from textured AlGaInP light-emitting diodes (LEDs) by using nanoimprint lithography.
The LED properties were characterized by electroluminescence and surface morphology was analyzed by optical microscope and scanning electron microscope. When comparing the textured and the conventional LED, we found that the surface-textured LED exhibits a 23% power intensity improvement at 20 mA. The dominant wavelength variation was under 1% and the voltage variation did not degrade. The output power improvement in the surface-textured LED can be attributed to the formation of Surface roughness structure at the top GaP surface. This textured surface enabled some light, outside of the escape cone (~17°), to escape through the semiconductor to air interface resulting in additional light extraction. These positive results indicate that high performance AlGaInP LEDs can be achieved by employing a Surface roughness structure
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