Au-Doped Indium Tin Oxide Ohmic Contacts to p-Type GaN

Indium tin oxide (ITO) thin films doped with Au, Ni, or Pt (3.5 at.% to 10.5 at.%) were deposited on p-GaN epilayers (Mg similar to 4 x 10(19) cm(-3)) using direct-current (DC) sputter codeposition. It was found that undoped ITO con- tacts to p-GaN exhibited leaky Schottky behavior, whereas the incorporation of a small amount of Au (3.5 at.% to 10.5 at.%) significantly improved their ohmic characteristics. Compared with standard Ni/ITO contacts, the Au-doped ITO contacts had a similar specific contact resistance in the low 10(-2) Omega cm(-2) range, but were more stable above 600A degrees C and more transparent at blue wavelengths. These results provide support for the use of Au-doped ITO ohmic contact to p-type GaN in high-brightness blue light-emitting diodes.