삼각형 질화갈륨 발광다이오드 제작 및 특성 연구

Abstract

Highly efficient GaN-based light-emitting diodes (LEDs) have been intensively developed in recent years for use in diverse applications, such as traffic lights, full color displays, backlighting unit of liquid crystal display (LCD), and solid-state lighting. This widespread application makes it desirable to increase the internal quantum efficiency and light extraction efficiency of LEDs. However, though recent crystal growth technology has improved the internal quantum efficiency, ηextraction still remains low because of the total internal reflection at the surface of LEDs due to the difference in refractive index between GaN (n = 2.5) and air (n = 1). To enhancement of the light extraction efficiency, several methods such as surface texturing, patterned sapphire substrate (PSS), chip shaping and photonic crystal have been proposed. Chip shaping is useful method to increase the extraction efficiency of LED by significant reduction in total internal reflection and increase in side wall emission with controlling the light path. In this work, we improve the efficiency of triangular shaped LED chip by optimizing the shape and electrode pattern design. We found that the extraction efficiency of LED with isoscale triangular shape is more higher than that of LED with equilateral triangle. In addition, we improve the electrical properties of LED with isoscale triangular shape by enhancing the current spreading with controlling the distance between n-electrode and p-electrode. The optical output power of LED with triangular shape is improved by 15.73 % as an input current of 100 mA without degradation of electrical properties, compared to that of LED with quadrangular shape. Therefore, this work shows that the triangular chip shaping is very important technique to fabricate the high efficient light emitting diodes.