Effects of surface treatment on the electrical properties of Ohmic contacts to (In)GaN for high performance optical devices

We investigate the effects of surface treatment on the Ohmic properties of the contacts to p-GaN and n-(In)GaN. I-V measurements show that for all the samples, the two-step surface treatment causes a large reduction in specific contact resistance. The I-V and XPS results show that for the Pt contacts to p-GaN, the two-step treatment using a BOE solution results in a reduction of SBH due to the effective removal of native oxide and the shift of the surface Fermi level toward the valence band edge. It is also shown that the two-step treatment using a HCl solution is very effective in improving the electrical and thermal properties of the Ti/Al contacts to n-(In)GaN. These results indicate that the two-step surface treatment can be a promising processing technique for optical devices.