Jyh-Chen CHEN¹, Gwo-Jiun SHEU¹, Farn-Shiun HWU^1,2, Hsueh-I CHEN¹, Jinn-Kong SHEU³, Tsung-Xian LEE⁴, and Ching-Cherng SUN⁴

¹Department of Mechanical Engineering, National Central University, Jhongli 32001, Taiwan
²Department of Mechanical Engineering, Nanya Institute of Technology, Jhongli 32091, Taiwan
³Institute of Electro-Optical Science and Engineering and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan
⁴Institute of Optical Sciences, National Central University, Jhongli 32001, Taiwan

(Received July 14, 2008; Accepted January 5, 2009)

The effects of current distribution in LED chips on the electrical potential and optical light extraction efficiency are investigated by a numerical simulation. The results show that when the resistivity of the current-spreading layer is decreased there is current-crowding near the n-contact. On the other hand, when the resistivity in the current-spreading layer increases, there is current-crowding near the p-contact. When the current is crowded near the n-contact due to less resistivity of the current-spreading layer, the input power is lower because of the smaller series resistance in the chip, and the light extraction efficiency is higher since the shadowing effect of the p-contact can be avoided. For L_p=50 μm in this study, the light extraction efficiency at ρ_ITO=0.1× 10^-3 Ω⋅cm is 1.4 times better than that when L_p=100 μm, even though the driving voltage is raised 1.02 times.

Key words: current-spreading, light-emitting diodes, indium tin oxide, numerical simulation, light extraction efficiency