W and WSi Ohmic contacts on both p- and n-type GaN have been annealed at temperatures from 300 to 1000°C. There is minimal reaction (≤100 Å broadening of the metal/GaN interface) even at 1000°C. Specific contact resistances in the 10-5 Ω cm2 range are obtained for WSix on Si-implanted GaN with a peak doping concentration of ∼5× 1020 cm-3, after annealing at 950°C. On p-GaN, leaky Schottky diode behavior is observed for W, WSix and Ni/Au contacts at room temperature, but true Ohmic characteristics are obtained at 250-300°C, where the specific contact resistances are, typically, in the 10-2 Ω cm2 range. The best contacts for W and WSix are obtained after 700°C annealing for periods of 30-120 s. The formation of β- W2N interfacial phases appear to be important in determining the contact quality.
|Number of pages||5|
|Journal||Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films|
|State||Published - 1999|