The microstructure of Ti/Au contacts on n-type GaN annealed in nitrogen
Ti(40nm)/Au(120nm) contacts have been prepared on n-GaN/sapphire. The contacts were annealed from 400C to 900C for 10min in nitrogen, respectively. The interaction between the contact metallization and the GaN epitaxial layer (on sapphire) was investigated by electron microscopy and X-ray diffraction. It was found that for an annealing at a temperature equal or higher than 700C, the gold diffused through Ti layer and Au-rich grains were formed under this Ti layer. Between the Au-rich grains and the n-type GaN layer a new Ti-rich thin layer was identified by XTEM. High resolution images and X-ray data showed that its TiN0.26 that was formed at the metal/semiconductor interface. FESEM investigations showed that Ti/Au contacts annealed in nitrogen still have a very smooth surface morphology.
contacts gan solid phase reaction transmission electron microscopy