Improved Thermal Stability of Ag Ohmic Contacts for GaN-Based Vertical Light-Emitting Diodes Using a Zn Capping Layer

Abstract

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 Ag/Zn contacts give higher output power than do LEDs with Ag only contacts. LEDs with the 500 degrees C-annealed Ag/Zn contacts exhibit 34% higher output power (at 20 mA) than LEDs with the 500 degrees C-annealed Ag only contacts. X-ray photoemission spectroscopy measurements are performed to describe the temperature dependence of the electrical properties of LEDs with the Ag/Zn contacts. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.002205esl] All rights reserved.