Low-Resistance and Reflective Ni/Rh and Ni/Au/Rh Contacts to p-GaN for Flip-Chip LEDs

摘要

We report on the formation of high-quality ohmic contacts to p-type GaN (4 X 10~(17) cm~3) using Ni (5 nm)/Rh (120 nm) and Ni (5 nm)/Au (5 nm)/Rh (120 nm) schemes for use in flip-chip light-emitting diodes (LEDs). Both the Ni/Rh and Ni/Au/Rh contacts become ohmic with specific contact resistances of 10~(-5) to 10~(-6) OMEGA cm~2, when annealed at 350 deg C for 2 min in air ambient. LEDs are fabricated using the Ni/Au/Rh and Ni/Au contact layers, which give a forward-bias voltage of 3.32 and 3.45 V at injection current of 20 mA, respectively. This indicates that the Rh-based contacts could be suitable for high power flip-chip LEDs.