Ag and zinc oxide-doped indium oxide ohmic contacts to p-type GaN for flip-chip LED applications

This work discusses Ag/zinc oxide-doped indium oxide (ZIO) and ZIO/Ag ohmic contacts to p-GaN for flip-chip light-emitting diode (LED) applications. Optimal conditions for Ag/ZIO and ZIO/Ag contacts are adopted to minimize the specific contact resistance to 1.74 x 10(-4) Omega cm(2) and 1.15 x 10(-3) Omega cm(2), respectively, as revealed by the transmission line model after heat treatment at alloying temperatures of 500 degrees C and 400 degrees C, respectively, for 10 min in air. Ag/ZIO contacts following treatment at 500 degrees C yield a reflectance of around 87% at a wavelength of 470 nm. GaN-based LEDs with Ag/ZIO contacts produced forward biases of 3.09 V at an injection current of 20 mA.