Improving the output power of near-ultraviolet InGaN/GaN-based light emitting diodes by enhancing the thermal and electrical properties of Ag-based reflector

Abstract

We report on the improved performance of near-ultraviolet (385 nm) InGaN/GaN multi-quantum well light emitting diodes (LEDs) by enhancing the thermal and electrical properties of Ag-based reflector. It is shown that after annealing at 500 degrees C, indium (In)-overlaid Ag contact exhibits considerably higher reflectivity at 385 nm than Ag only contact. After annealing at 500 degrees C, both the Ag only and In-overlaid Ag contacts are ohmic with a specific contact resistance of 6.7 x 10(-4) and 8.7 x 10(-5) Omega cm(2), respectively. Near-UV (385 nm) LEDs fabricated with annealed Ag only and In-overlaid Ag reflectors show a forward-bias voltage of 3.4 and 3.37 V at an injection current of 20 mA, respectively. The LEDs with the annealed In-overlaid Ag reflector exhibit 24.7% higher light output power (at 20 mA) than the LEDs with the 500 degrees C-annealed Ag only reflector. X-ray photoemission spectroscopy was performed to understand the improved electrical properties of the In-overlaid Ag reflectors. The enhanced thermal stability of In-overlaid Ag reflector is also briefly described. (C) 2013 Elsevier Ltd. All rights reserved.