Improved light extraction in AlGaInP-based LEDs using a roughened window layer

Abstract

Surface-textured p-GaP/AlGaInP/GaAs light-emitting diodes (LEDs) have been fabricated using a combination of natural lithography and dry etching techniques. Here, the randomly positioned polystyrene spheres are used as a mask for dry etching. The p-GaP window layer was successfully etched to achieve nanopillars on its surface. It was found that the surface-textured LEDs with the p-GaP nanopillars revealing a diameter of 300-320 nm, a density of 1.4 x 10(9) cm(-2), and a depth of 550-650 nm have maximum luminance intensity. Output power of the surface-textured LED increased about 70% compared with the planar-surface LED at a forward current of 20 mA. The LED window with nanopillar diameter (300-320 nm, half of wavelength) and depth (600 nm, similar to wavelength) resulting in much light extraction compared with flat-surface LEDs or deeper nanopillars has been demonstrated by experiment and simulation. After a 1000 h aging test, luminance intensity and voltage fluctuation do not exceed +/- 10%. These results indicated that AlGaInP-based LEDs with a roughened surface did not exhibit deteriorated performance.