Investigations on the Origin of the Ohmic Behavior for Ti/Al Based Contacts on n-Type GaN

This work reports of investigation on the origin of the ohmic behavior for Ti/Al basedcontacts on n-GaN. Indeed, last publications tend to prove that the ''nitrogen vacancy'' theory is notconfirmed by the experimental ground available. To find new answers, we first made electrical charac-terizations on some Al/Ti/n+-GaN contacts with different annealing conditions. Then, we performedSIMS depth profiles of annealed TiN/Ti/n+-GaN samples. Results developed in this paper tend todemonstrate that the ohmic behavior of Ti/Al based contact is mainly due to an increase of the dop-ing concentration. Moreover, the high doping level can be explained by an in-diffusion of Ti and anexo-diffusion of Si elements close to the metal / semiconductor interface.