Catalytic role of Au in Ni/Au contact on GaN(0001)

Abstract

We investigated the structural behavior of the Ni/Au contact on GaN(0001) and found the catalytic role of Au during annealing, using in situ x-ray scattering. The oxidation kinetics of Ni during annealing in air was greatly affected by the presence of Au. The accelerated GaN decomposition and Ni nitride formation during annealing in N2 also provide evidence of the catalytic role of Au. The results suggest that oxidized Ni/Au ohmic contact exhibit better thermal stability than that of the N2 annealed Ni/Au contacts.

Metal/GaN reaction chemistry and their electrical properties

“…The multiplied intensities are therefore directly related with the number of Ga elements diffused out to the surface from the metal/GaN interface. The result indicates that GaN decomposition is much accelerated in the alloyed contacts of Au/Ni/GaN and Pt/Ni/GaN, which is consistent with our previous results [12]. We note that Ga signal is detected in Ni and Au single-layer contacts even though it is small.…”

Au Catalyzed Structural and Electrical Evolution of Ni/Au Contact to GaN

“…2b. Instead, almost all of the Ni atoms are in the Ni-O form [11]. Even though the weak NiO signal is hardly seen in Fig.…”

“…First the reaction of Ni oxidation during annealing in air is also accelerated by the presence of Au. Interestingly, the NiO phase is preferentially formed at the lower temperature of 500 C [11]. Once the Ni-O bonding is formed, it would be then hardly decomposed for the reaction with N at the temperature of 550 C, which is not high enough considering the melting point of NiO, 1960 C. By the formation of the strong Ni-O bonding, we argue that the Ni-N reaction is suppressed in the air annealed Ni/Au contact.…”

“…The Ni 4 N phase begins to form at 500 C and its growth is clearly shown at the higher temperature of 550 C. The Ni 4 N phase, which is believed to be a high temperature compound, deteriorates the contact resistivity of the Ni/Au layer on p-type GaN films and its formation should be therefore avoided [9,10]. Recently, it has been reported that the kinetics of the formation of the Ni 4 N phase in N 2 annealing of Ni/Au contact is catalytically activated by Au [11]. The accelerated formation Fig.…”

Oxidation treatment on Ni/Au Ohmic contacts to p‐type GaN

“…Metal Ni plays a role in removing the contamination on the GaN surface [10]. The existence of Au at the interface of metal/p-GaN should catalyze the above reactions [7].…”