Ohmic Contact Formation on N-Polar n-GaN Surfaces Exposed by Wafer Bonding and Back Surface Process

We expose N-polar surfaces of n-GaN layers epitaxially grown on Si (111) substrates by wafer bonding their Ga-polar surfaces and applying the back surface process, and form ohmic contacts on their N-polar surfaces by evaporating Ti/Al/Ti/Au and annealing. The contact resistance for the N-polar surfaces is approximately over 100 times higher than that for the Ga-polar surfaces of the same n-GaN layers, which suggests that the wafer bonding technologies are promising for fabricating advanced devices on N-polar surfaces.