TiAlNiAu contacts for ultrathin AlN/GaN high electron mobility transistor structures

The morphology of ultrathin AlN/GaN high electron mobility transistors without or with TiAlNiAu Ohmic contacts is examined by using transmission electron microscopy and associated analytical methods. The contact inclusion (CI) density has increased with increasing annealing temperature but the lowest specific contact resistivity is obtained for structures annealed at 850 [degree]C and the AlN layers have remained intact in dislocation-free areas of all samples.