Ni layer thickness and Ni layer annealing process which affect Ni/ITO-p-GaN ohmic contact were studied through CTLM

I-V

curve

surface morphology

optical data etc.It was found that the Ni layer can help the formation of ohmic contact for ITO/GaN and the contact resistance reduced at first and then increased with the thickness of Ni layer.The best ohmic contact electrode was got with Ni layer thickness of 6 nm

while the contact resistance of Ni/ITO on p-GaN was 9.5×10

-5

Ω·cm

2

and the transmittance could reach 74% at 470 nm.This result without high temperature annealing indicated that too much thick of Ni layer is bad for the formation of NiO which could be related to low-resistance ohmic contact.How the Ni layer affect ohmic contact through annealing to Ni layer directly at oxide atmosphere was studied.The experiment showed that the contact resistances increase with annealing temperature.The NiO could be helpful to the formation for ohmic contact.But if the intermediate semiconductor layer(ISL) can't reduce the Schottky barrier height(SBH) of Ni/GaN interface much

the contact resistance will increase.It is easy for carrier injection where there is Niatom

which can promote the character of ohmic contact better.According to the experiment results

a new method named low temperature(L-T) oxided Ni layer was proposed.This method can reduce ohmic contact resistance

better surface morphology and improve reliability of LED device.