Optimizing surface morphology of ohmic contacts on GaN high electron mobility transistors continues to be a challenge in the GaN electronics industry. In this study, a variety of metal schemes were tested under various annealing conditions to obtain contacts with optimal qualities. A Ti/Al/Ti/Ni/Au (20/120/40/60/50 nm) metal scheme demonstrated the lowest contact resistance (Rc) and a smooth surface morphology, and the mechanisms were investigated by materials analysis. A Ti/Al/Ti/Ni/Au metal scheme with optimized Ti and Ni thicknesses can result in formation of a larger proportion of Al-Ni intermetallics and a continuous TiN interlayer, which results in smooth surface and low Rc.
|Journal||Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics|
|State||Published - 1 Jan 2014|