Enhancement Of Extraction Efficiency Of Red LED Via Surface Roughening

In recent years, the development of GaP-LEDs is rapid, but its low external quantumefficiency seriously restricts its wide application in semiconductor lighting area. This articlefocused on how to improve the red LED luminous efficiency. By roughening the surface ofthe GaP-based LED, changing the direction of the propagation of light that satisfy the law ofthe whole reflection of the light, so that the light emitted the other surface or reflected back tothe original surface, and thus light is not totally reflected by the interface, thus improving theefficiency of the LED light.In this paper, the red LED on the wafer surface was roughened via wet etching and dryetching. The surface roughening morphology of the LED epitaxial wafer was influenced bymolten KOH and KOH-ethylene glycol solution, respectively, at different temperatures anddifferent times. And the relative performance (morphology, I-V characteristic curves,brightness and dominant wavelength) of LED devices were characterized by an atomic forcemicroscope (AFM) and semiconductor chip automatic characterization system. The brightnessand current characteristics of roughening and non-roughening devices were compared. Theresults showed that this method of using molten KOH to rough LED epitaxial wafers caneffectively suppressed the total reflection of the light through the interface of LED surfaceand air. Experimental results show that the luminous efficiency of the red LED epitaxial waferimproved about32.7%, after etching in200℃, molten KOH for8min. Using KOH-ethyleneglycol solution at a temperature of roughening200℃, when coarse time was12min, theluminous efficiency of the produced device increased35%. And using the ICP etched wafer,we studied the relationship between the size of etching pits and the luminous intensity, thetime of etching pits was1.5μm, the intensity of light emitting device improved28%.