Ohmic Contact to P-Type GaN

Investigations of the new metal scheme for ohmic contact to p-GaN have been carried out. The specific contact resistance was measured to be ρ c =3.6×10 -3 Ω cm 2 which is the lowest value ever reported for moderately doped p-GaN (4.4×10 17 /cm 3 ). All metals were deposited on metalorganic chemical vapour deposition (MOCVD) grown p-GaN. The interaction mechanism between Ni and p-GaN has been investigated. Zn diffusion has been observed during annealing in Au–Zn/Ni on p-GaN. The interfacial reaction mechanism during annealing has been studied by secondary ion mass spectroscopy (SIMS) measurement. From this measurement, it is observed that Ni dissociates at the p-GaN surface and this dissociation promotes the Zn diffusion upon heat treatment. The electrical properties were studied using current–voltage ( I – V ) measurements at room temperature. The microstructure between the Ni and p-GaN interface was investigated using high-resolution transmission electron microscopy (TEM) before and after the heat treatment.