Journal of the Korean Physical Society

pISSN 0374-4884 eISSN 1976-8524


Cross-Disciplinary Physics and Related Areas of Science and Technology

J. Korean Phy. Soc. 2011; 59(1): 156-160

Published online July 15, 2011

Copyright © The Korean Physical Society.

Thermally Stable and Reflective RhZn/Ag Ohmic Contacts to p-type GaN for Near-UV Flip-chip Light-emitting Diodes

Seong-Han Park, Joon-Woo Jeon, Tae-Yeon Seong, Jeong-Tak Oh


We investigated Rh-Zn solid solution (3 nm)/Ag(200 nm) schemes in order to produce thermally stable and low-resistance p-type Ohmic reflectors for high-performance flip-chip light-emitting diodes (LEDs). The Rh-Zn solid solution/Ag contacts show a specific contact resistance of 1.2 ¡¿ 10−4 ¥Øcm2 and a reflectance of about 78% at a wavelength of 395 nm when annealed at 500 ¡É for 1 min in air. Scanning electron microscopy results show that unlike Ag only contacts, the Rh-Zn solid solution/Ag contacts experience insignificant morphological degradation even after annealing at 500 ¡É for 1 min. Near-UV InGaN/GaN LEDs (1200 ¡¿ 600 ¥ìm2 in chip size) fabricated with the annealed Rh-Zn solid solution/Ag reflectors give a forward-bias voltage of 3.43 V at an injection current of 80 mA, which is lower than that (3.65 V) of LEDs with Ag only reflectors. LEDs with the annealed RhZn solid solution/Ag reflectors exhibit 43% higher light output power (at 80 mA) than the LEDs with annealed Ag contacts. X-ray photoemission spectroscopy examinations were performed to investigate possible Ohmic formation behaviors.

Keywords: Ohmic reflector, Ag, Rhodium-zinc solid solution, Light emitting diode,