Effects of ITO Pattern on the Electrical and Optical Characteristics of LEDs

We studied on the effects of patterned indium-tin oxide (ITO) on the electrical and optical characteristics of GaN-based light-emitting diodes (LEDs) in detail. In our experiment, LEDs with varied patterned ITO layers are fabricated. The electrical and optical characteristics are analyzed through the diode equation and 3D electro-thermal simulation, the rate equation and Monte-Carlo ray-tracing simulation, respectively. The analysis results indicate that the light output power (LOP) of the LEDs with patterned ITO achieve an enhancement of 12.7% compared to that of the LEDs with planar ITO. Moreover, the series resistance and ideality factor are the minimum when ITO is planar, and will increase with spacing of ITO pattern decreasing due to the degeneration of current spreading and ohmic contact. However, the light extraction efficiency (LEE) is smaller for LEDs with planar ITO and will increase with spacing decreasing, which is due to the increase of probability of photon redirecting and escaping. These analysis results are helpful to understand the effects of ITO pattern on electrical and optical characteristics and therefore to design an optimal pattern structure. (C) 2012 The Electrochemical Society. All rights reserved.