High-Quality AlN Film Grown on Sputtered AlN/Sapphire via Growth-Mode Modification

Heteroepitaxy of high-quality AlN film is the key to advance the prosperity of deep-ultraviolet (DUV) devices when a large-size and low-cost native substrate is unavailable. Here, we proposed a strategy to obtain high-quality AlN film by combining growth-mode modification with sputtered AlN buffer using metal-organic chemical vapor deposition (MOCVD). Compared with the MOCVD AlN buffer, the sputtered AlN buffer consists of smaller and more uniform grains with better c-axis orientation, leading to a better growth-mode modification in the subsequent growth process. On one hand, the better c-axis orientation is inherited by the upper AlN epilayer, resulting in a lower screw dislocation density. On the other hand, the better growth-mode modification significantly suppresses edge dislocations by producing high-density nanoscale voids and many 90 degrees bent dislocations. Therefore, the total threading dislocation density of the AlN film grown on the sputtered AlN buffer is dramatically reduced to an extremely low value of 4.7 X 10(7) cm(-2), which is 81.2% less than that of the AlN film grown on the MOCVD AlN buffer. This very simple yet effective technique demonstrates great potential for the mass-fabrication of low-cost and high-performance DUV devices.