Improved thermal stability of Ag ohmic contacts for GaN-based vertical light-emitting diodes using a Zn capping layer

We report on the improvement of the thermal stability of Ag ohmic contacts for high-power GaN-based vertical light-emitting diodes (LEDs) using a Zn capping layer. The 20-nm-thick Zn capping layer suppresses agglomeration by forming ZnO. Blue LEDs fabricated with the AgZn contacts give higher output power than do LEDs with Ag only contacts. LEDs with the 500C-annealed AgZn contacts exhibit 34 higher output power (at 20 mA) than LEDs with the 500C-annealed Ag only contacts. X-ray photoemission spectroscopy measurements are performed to describe the temperature dependence of the electrical properties of LEDs with the AgZn contacts.