Ohmic contacts to n-GaN using PtIn2

A new metallization scheme has been developed to form Ohmic contacts to n-GaN. Contacts were fabricated by sputtering the intermetallic compound, PtIn2 on metal–organic vapor phase epitaxy grown n-GaN (n∼5×1017 cm−3) with some of the contacts subjected to rapid thermal annealing. Contacts in the as-deposited state exhibited nearly Ohmic behavior with a specific contact resistance of 1.2×10−2 Ω cm2. Contacts subjected to rapid thermal annealing at 800 °C for 1 min exhibited linear current–voltage characteristics and had specific contact resistances less than 1×10−3 Ω cm2. Auger depth profiling and glancing angle x-ray diffraction were used to examine the interfacial reactions of the PtIn2/n-GaN contacts. Consistent with estimated phase diagram information, the results from Auger depth profiling and glancing angle x-ray diffraction indicated the formation of (InxGa1−x)N at the contact interface, which could be responsible for the Ohmic behavior of PtIn2 contacts.