Mechanism for Ohmic contact formation of Ti on <i>n</i>-type GaN investigated using synchrotron radiation photoemission spectroscopy

Changes of the work function of contact metal and the atomic composition at the vicinity of metal/GaN interface were studied in in situ annealed Ti on n-type GaN using synchrotron radiation photoemission spectroscopy. Ti layer transformed to TiN and its work function increased as annealing temperature increased. Meanwhile, the atomic composition ratio of Ga-to-N below the TiN contact increased indicating the creation of N vacancies. This provides evidence that N vacancies produced below the contact, acting as donors for electrons, play a main role in forming the Ohmic contact.