Further improvement in the light output power of InGaN-based light emitting diodes by reflective current blocking design

Abstract

In this study, the fabrication and characterization of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with further improvement by the design of a reflective current blocking layer (CBL) were described, and these are demonstrated to be an inexpensive and feasible way for improving the performance of LEDs. With the reflective CBL, not only was the injected current forced to spread outside instead of flowing directly downward under a p-pad, but the light generated from the active region could also be extracted outside of the LED by reflection under the p-pad. At 20 mA, as compared to the conventional LED, the light output power of the LEDs with the normal and reflective CBL can be increased by 15.7% and 25.8%, respectively. We found that the forward voltages of the LEDs with CBL structure were both about 3.7 V at 20 mA, which was slightly higher than that of the conventional LED (3.6 V). In our experiment, the further increase in the light output power of the reflective CBL LED could be attributed to more current injection into the light-emitting active region outside of the p-pad by the CBL and a reduction in optical absorption at the p-pad with more extraction by the reflective design.