Improvement of brightness with Al2O3 passivation layers on the surface of InGaN/GaN-based light-emitting diode chips

In this study, sputtered 50, 70 and 90 nm thick Al2O3 thin films were evaluated as a passivation layer in the process of InGaN-based blue as LEDs (Light-Emitting Diodes) in order to improve the brightness of LED lamps. For packaged LED lamps, lamps with Al2O3 passivation layer had higher brightness than ones with SiO2 passivation layer, and LED lamps with 90-nm Al2O3 passivation layer were the brightest among four kinds of lamps. Although lamps with Al2O3 passivation layer had a bias voltage 0.25 V at 20 mA forward current higher the lamps built with SiO2 passivation layer, their brightness was improved about 13.6% higher than the conventional LEDs with no change in emitting wavelength.