Enhanced thermal stability of Ag ohmic reflector for InGaN/GaN light-emitting diode using a Ru capping layer |
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Authors: | Jae-Seong Park Joon-Woo Jeon Chang-Hyung Lee Chang-Hoon Choi Sungho Jin Tae-Yeon Seong |
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Institution: | 1. Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea;2. Materials Science Program, Department of Mechanical & Aerospace Engineering, UC San Diego, La Jolla, CA 92093, USA |
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Abstract: | A Ru capping layer is employed to improve the thermal stability of Ag ohmic reflectors for high-power GaN-based light-emitting diodes (LEDs). The 20-nm-thick Ru capping layer is shown to be fairly effective in suppressing agglomeration by forming RuO2. The Ag/Ru contacts exhibit specific contact resistance of 8.1 × 10−5 Ω cm2 and reflectance of ∼89% at a wavelength of 450 nm when annealed at 500 °C for 1 min, which are much better than that of Ag only contacts. Blue LEDs fabricated with the 500 °C-annealed Ag/Ru contacts give a forward voltage of 2.98 V at an injection current of 20 mA, which is lower than that (3.02 V) of LEDs with the 500 °C-annealed Ag only contacts. LEDs with the 500 °C-annealed Ag/Ru contacts show 25% higher output power (at 20 mA) than LEDs with the 500 °C-annealed Ag only contacts. X-ray photoemission spectroscopy examinations are performed to describe the improved electrical performance of the Ag/Ru contacts. |
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Keywords: | Light-emitting diode A Ru capping layer Ag ohmic reflector GaN |
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