Low-Defect-Density Aluminum Nitride (AlN) Thin Films Realized by Zigzag Macrostep-Induced Dislocation Redirection
Chenguang He, Hualong Wu, Chuanyu Jia, Kang Zhang, Longfei He, Qiao Wang, Junze Li, Ningyang Liu, Shan Zhang, Wei Zhao, Zhitao Chen, Bo Shen
Abstract
Owing to the lack of large-diameter and affordable AlN bulk crystals, high-quality AlN films grown on sapphire substrates have been intensively analyzed for the potential applications in optoelectronic and electronic devices. Herein, we successfully fabricated low-defect-density AlN thin films on large-offcut-angle sapphire substrates combining magnetron sputtering and metal–organic chemical vapor deposition. It is found that the crystalline qualities of AlN films strongly depend on the densities and geometric features of atomic steps. When high-density zigzag macrosteps are formed on the surface, they can induce dislocation inclination toward multiple directions rather than a single one. In this situation, the inclined dislocations can interact with not only vertical dislocations but also other inclined dislocations. Profiting from the large inclination angles (30–78°), the lateral interaction range of dislocations exhibits a 6-fold increase at most, leading to more frequent dislocation interactions within a relatively thin layer. As a result, the threading dislocation density value of 1 μm thick AlN is reduced down to 1.4 × 109 cm–2, demonstrating an 80% decrease in comparison with its counterpart without the macrostep-induced dislocation redirection effect. This approach is expected to boost the development of low-cost and high-performance devices on AlN/sapphire templates.