Electrical-optical analysis of a GaN/sapphire LED chip by considering the resistivity of the current-spreading layer

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.