A p-type ohmic electrode in a gallium nitride based(GaN based) optical
device and a fabrication method thereof. The p-type ohmic electrode in a
GaN based optical device is fabricated using a rutile structure
transition metal layer, such as an Ru, Ir or Os layer, or an oxide layer
thereof, or using a double layer comprised of an Ru layer as a base layer
and an Ni layer, an ITO layer or an AuO layer on the Ru layer. Thus, the
p-type ohmic electrode is good in light transmittance and is thermally
stable while having low contact resistance with the p-GaN layer.