Effect of the Electrode Pattern on Current Spreading and Driving Voltage in a GaN/Sapphire LED Chip 李仁凱

Outline Introduction Introduction Results and Discussion Results and Discussion Conclusions Conclusions References References

Introduction The numerical results current distributions for the striped pattern p- electrode are well consistent with the optical emission patterns taken from emission images. A desirable uniformity of the current distribution in the active layer can be obtained by the appropriate arrangement of p- and n-electrode patterns.

Results and Discussion Figure 1. Shematic illustration of a cross-sectional view of the device along the stripe direction.

Results and Discussion Figure 3. Micrographs of experimental optical emissions when operated at 30 mA for (a) the short-stripe case and (b) the long-stripe case. The related chip dimensions are also marked.

Results and Discussion Figure 2. Relation of input power to (a) driving voltage and (b) wall-plug efficiency for both short- and long stripe LED from the experiments.

Results and Discussion Figure 4. Isoline diagrams of simulated current densities in the active layer when operated at 30 mA for (a) the short-stripe case and (b) the long- stripe case.

Results and Discussion Figure 5. Normalized experimental optical emission densities solid symbols and currents from the simulation hollow symbols along the line bar in Fig. 3 at 20 mA squares and 30 mA triangles for a the short-stripe case and b the long-stripe case.

Results and Discussion Figure 6. Top view of the simulated current vectors of the ITO, p-GaN, and n-GaN layers when operated at 30 mA for (a) the short stripe case and (b) the long-stripe case.

Results and Discussion Figure 7. Simulated relations of the p-electrode stripe length to current density in the active layer and the driving voltage of the LED at an input current of 30 mA. The difference between the maximum and minimum current density and the standard deviation of current density in the active layer are marked by hollow and solid squares, respectively. The driving voltage of the LED is marked by solid circular symbols. The inset isoline diagram shows the calculated current density distribution in the active layer for a stripe length of 285 μ m.

Results and Discussion Figure 8. (a) Lengths of the n-electrode around the chip marked from no. 1 to no. 9; top view of the 3D current vectors in the n-GaN layers at 30 mA from the simulation when the n- electrode length reaches the (b) no. 2, © no. 6, and (e) no. 9 positions, respectively. (d) A cross-sectional view along the AB line in (c ).

Results and Discussion Figure 9. Relations of different n-electrode lengths to current density in the active layer and the driving voltage of the LED at an input current of 30 mA from the simulation.

Results and Discussion Figure 10. (a) Diagram of the p- and n-electrode patterns, and (b) 3D current arrows in the active layer for the no. 6 length n-electrode when operated at 30 mA from the simulation.

Results and Discussion Figure 11. Relations of different n-electrode lengths with the current density in the active layer and driving voltage of the LED at an input current of 30 mA from the simulation for the p- and n-electrode patterns in Fig. 10a.

Conclusions A numerical simulation has been performed to investigate the effects of p and n-electrode patterns on the current spreading and the driving voltage of side-view GaN/sapphire LED chips. The influence of changing the p-electrode pattern on the current spreading and the voltage drop is more significant than that made by altering the n-electrode pattern.

References “Effect of the Electrode Pattern on Current Spreading and Driving Voltage in a GaN/Sapphire LED Chip” Gwo-Jiun Sheu, Farn-Shiun Hwu, Jyh-Chen Chen, Jinn-Kong Sheu, and Wei-Chi Lai, Journal of The Electrochemical Society, H836-H 。 “Effect of the Electrode Pattern on Current Spreading and Driving Voltage in a GaN/Sapphire LED Chip” Gwo-Jiun Sheu, Farn-Shiun Hwu, Jyh-Chen Chen, Jinn-Kong Sheu, and Wei-Chi Lai, Journal of The Electrochemical Society, H836-H 。