IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Monday Sessions
       Session SC-MoA

Paper SC-MoA10
Ni/Au Ohmic Contacts to p-GaN Epilayers

Monday, October 29, 2001, 5:00 pm, Room 124

Session: GaN Surfaces, Interfaces, and Devices
Presenter: P.H. Holloway, University of Florida
Authors: B. Liu, University of Florida
E. Lambers, University of Florida
P.H. Holloway, University of Florida
T. Johnson, Uniroyal Optoelectronics
D. Guiterrez, Uniroyal Optoelectronics
K. Kidney, Uniroyal Optoelectronics
W.B. Alexander, Uniroyal Optoelectronics
Correspondent: Click to Email
The deposition and properties of evaporated thin Ni (5 nm)/Au (5 nm) contacts on MOCVD p-GaN has been studied. After annealing the bi-layer structure in an oxidizing environment, the contact is transformed from a Schottky to an ohmic behavior. The Ni underlying the Au top layer was found to have largely diffused to the surface and formed NiO during the anneal. The Au formed a porous film between the NiO and p-GaN which allowed between 50 and 85% transmission of 450 nm light, depending upon the deposition and annealing conditions. The porous Au network also allowed good sheet resistance with typical values of 300 @ohm@. X-ray photoelectron spectroscopy indicated that the NiO reached to the GaN interface, however a Ni-Ga-Au ternary metallic phase also formed at the interface. This phase modified the capillary forces and resulted in formation of the porous Au network. In the absence of this metallic phase, the Au film broke into islands with a very high sheet resistance. Formation of the porous network will be discussed in terms of a total energy model of thin film morphology. The consequences of forming NiO and forming the ternary metallic layer upon achieving an ohmic contact will also be discussed.