Optimal Growth Conditions for Forming -Axis (002) Aluminum Nitride Thin Films as a Buffer Layer for Hexagonal Gallium Nitride Thin Films Produced with In Situ Continual Radio Frequency Sputtering.

Aluminum nitride (AlN) thin-film materials possess a wide energy gap; thus, they are suitable for use in various optoelectronic devices. In this study, AlN thin films were deposited using radio frequency magnetron sputtering with an Al sputtering target and N as the reactive gas. The N working gas flow rate was varied among 20, 30, and 40 sccm to optimize the AlN thin film growth. The optimal AlN thin film was produced with 40 sccm N flow at 500 W under 100% N gas and at 600 °C. The films were studied using X-ray diffraction and had (002) phase orientation. X-ray photoelectron spectroscopy was used to determine the atomic content of the optimal film to be Al, 32%; N, 52%; and O, 12% at 100 nm beneath the surface of the thin film. The film was also investigated through atomic force microscopy and had a root mean square roughness of 2.57 nm and a hardness of 76.21 GPa. Finally, in situ continual sputtering was used to produce a gallium nitride (GaN) layer on Si with the AlN thin film as a buffer layer. The AlN thin films investigated in this study have excellent material properties, and the proposed process could be a less expensive method of growing high-quality GaN thin films for various applications in GaN-based power transistors and Si integrated circuits.