12 October 2009 Removal and passivation of surface defects in perforated GaN-based light-emitting diodes
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Perforated GaN-based light-emitting diodes (LEDs) with an array of plasma-etched microholes penetrating through the active region were fabricated using lithography and plasma etching. Plasma damage on the microhole sidewalls led to an increase in junction leakage by up to seven orders of magnitude and a reduced light emission in the low injection regime. It was found that KOH can etch off the plasma-damaged materials, leading to a complete suppression of surface leakage currents. It however attacked metal contacts and increased the forward turn-on voltage. Thermal annealing removed damage in the near-surface bulk region, whereas (NH4)2S treatment only passivated the defect states at the immediate surfaces. Both methods produced a partial restoration of the forward-bias characteristics. It has been demonstrated that annealing at 700 °C used in conjunction with prolonged sulfide passivation can remove or passivate all plasma-induced defects and result in a complete suppression of surface leakage in the perforated LEDs. This work is an important step toward developing high-efficiency photonic crystal-integrated LEDs, in which light can only be coupled to radiation modes but the undesirable guided light emission is inhibited.
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Y. Yang, Y. Yang, X. A. Cao, X. A. Cao, } "Removal and passivation of surface defects in perforated GaN-based light-emitting diodes", Proc. SPIE 7518, Photonics and Optoelectronics Meetings (POEM) 2009: Solar Cells, Solid State Lighting, and Information Display Technologies, 75180V (12 October 2009); doi: 10.1117/12.841361; https://doi.org/10.1117/12.841361


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