Improved Performance of High-Voltage Vertical GaN LEDs via Modification of Micro-Cell Geometry
AbstractVertical-type high-voltage light-emitting diodes (HV-LEDs) with 2 × 2 micro-cells were fabricated on Cu substrates, and the micro-cell geometry was modified to enhance the optoelectronic performance. The current spreading in micro-cell is most dominantly affected by the distance between electrode and edge of chip. When square cells were combined in a HV-LED, the device performance was poor due to an obvious current-crowding phenomenon that occurred near the electrodes. This was attributed that the electrodes in these four square micro-cells were all far away from the edges, resulting in the severe current-crowding phenomenon. On the contrary, as the HV-LED was prepared with four rectangle, triangle, or L-shaped micro-cells, the electrodes were close to the edges of micro-cells and the current spreading effect can be easily improved. Although a HV-LED connected with L-shaped cells possessed a better current spreading effect and a lower surface temperature, the light extraction was relatively low because of an electrode-shading loss effect. When triangular cells were used to prepare the HV-LED, the device achieved a superior optoelectronic performance compared with that of other cells because of a lower current-crowding effect and a more uniform light emission. After an epoxy package process, a lower forward voltage of 14.9 V and a higher output power of 353.2 mW were obtained using this HV-LED at an injection current of 80 mA. Additionally, the wall-plug efficiencies of this device at 20 and 80 mA were 41.1% and 29.7%, respectively. The results confirm that the design of triangular cell is beneficial for enhancing the optoelectronic performance of HV-LEDs. Furthermore, the fabrication processes of vertical LEDs have high potential for HV-LED applications. View Full-Text
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Wu, P.-C.; Ou, S.-L.; Horng, R.-H.; Wuu, D.-S. Improved Performance of High-Voltage Vertical GaN LEDs via Modification of Micro-Cell Geometry. Appl. Sci. 2017, 7, 506.
Wu P-C, Ou S-L, Horng R-H, Wuu D-S. Improved Performance of High-Voltage Vertical GaN LEDs via Modification of Micro-Cell Geometry. Applied Sciences. 2017; 7(6):506.Chicago/Turabian Style
Wu, Ping-Chen; Ou, Sin-Liang; Horng, Ray-Hua; Wuu, Dong-Sing. 2017. "Improved Performance of High-Voltage Vertical GaN LEDs via Modification of Micro-Cell Geometry." Appl. Sci. 7, no. 6: 506.