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The N-polar face of the GaN high electron mobility transistor (HEMT) is capable of forming a low-resistivity ohmic contact. However, few reports to date describe the process of fabricating N-polar GaN HEMTs. In the present study, we investigated the dependence of the contact electrode metal resistance on the annealing temperature. A circular transmission line model was used to measure the contact resistance. Low resistances of 10 −5 -10 −6 Ω cm 2 in the as-deposited state were observed. Contact characteristics following the annealing treatment deteriorated at low temperatures and improved again at high temperatures. This tendency is possibly related to the thin oxide layer at the interface between Ti and GaN. Using Ti/Al/Ti/Au electrodes of 20/100/10/50 nm, we observed a contact resistivity of 2.9 × 10 −6 Ω cm 2 after annealing at 775 °C.

The growth of graphene on 3C-SiC/Si heterostructure is a promising approach, which provides low production cost, high scalability and easiness of nanoelectromechanical system fabrication. However, the quality of graphene is still insufficient for device applications due to mediocre morphological and structural quality of the 3C-SiC epilayers compared to bulk SiC crystals and to excessive Si out-diffusion from the Si substrate. Here, we propose a solution of inserting a 4H-AlN layer between 3C-SiC and Si, which allows us to polish the 3C-SiC film without worrying about enhancement of the Si out-diffusion despite the thinning after the polishing. With this insertion, a considerable quality improvement is achieved in our graphene on silicon.

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