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 400°C to 900°C 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 700°C, 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 it is 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. Ti(40nm)/Au(120nm) contacts have been prepared on n-GaN/sapphire. The contacts were annealed from 400°C to 900°C 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 700°C, 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 it’s 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.