Enhanced output power of InGaN-GaN light-emitting diodes with high-transparency nickel-oxide-indium-tin-oxide Ohmic contacts

Abstract

This study develops a highly transparent nickel-oxide (NiO )-indium-tin-oxide (ITO) transparent Ohmic contact with excellent current spreading for -GaN to increase the optical output power of nitride-based light-emitting diodes (LEDs). The NiO -ITO transparent Ohmic contact layer was prepared by electron beam in-situ evaporation without postdeposition annealing. Notably, the transmittance of the NiO -ITO exceeds 90% throughout the visible region of the spectrum and approaches 98% at 470 nm. Moreover, GaN LED chips with dimensions of 300 300 m fabricated with the NiO -ITO transparent Ohmic contact were developed and produced a low forward voltage of 3.4 V under a nominal forward current of 20 mA and a high optical output power of 6.6 mW. The experimental results indicate that NiO -ITO bilayer Ohmic contact with excellent current spreading and high transparency is suitable for fabricating high-brightness GaN-based light-emitting devices.

Enhancing the light extraction efficiency of GaN-based LEDs

“…Ohmic contact with excellent current spreading for p-GaN to increase the optical output power of GaN-based LEDs was developed by Pan et al [26] . An increase of 38% in output power of the GaN-based LED with NiO x -ITO contact compared with conventional Ni-Au contact was obtained.…”

Bevelled-sidewalls formation and its effect on the light output of GaInN MQW LED chips

“…The large difference in the refractive index between semiconductor and air is such that a significant gap exists between the internal quantum efficiency of LEDs and their external quantum efficiency. Therefore, very much study has focused on improving the external quantum efficiency of GaN LED, such like pattern substrate [3], surface roughing [4,5,6] and wafer bonding with metal reflector at the interface [7].…”