| abstract |
A method of forming a light-transmissive contact on a p-type Gallium nitride (GaN) layer of an optoelectronic device includes in one embodiment, introducing a selected metal in an oxidized condition, rather than oxidizing the metal only after it has been deposited on the surface of the p-type GaN layer. In some applications, the oxidized metal provides sufficient lateral conductivity to eliminate the conventional requirement of a second highly conductive contact metal, such as gold. If the second contact metal is desired, an anneal in an oxygen-free environment is performed after deposition of the second layer. The anneal causes the second metal to penetrate the oxidized metal and to fuse to the surface of the p-type GaN layer. In a second embodiment, the oxidation occurs only after at least one of the two metals is deposited on the surface of the p-type GaN layer. In one application of the second embodiment, the two metals are deposited and the oxidation occurs in an environment that includes both water vapor and oxygen gas. In an alternative application of the second embodiment, the first metallic layer is deposited and then oxidized throughout its depth. The second material, such as gold, is evaporated on the first material and a re-anneal step is performed to drive the second metal through the oxidized first metal. In any of the applications of either embodiment, a pattern of windows may be formed in the resulting contact structure or in additional layers that are formed thereon. |