Characterization of GaN grown on Si substrate with sputtering AlN buffer layer by molecular beam epitaxy

This study reports the characterization of GaN grown on Si substrate with sputtering AlN buffer layer by plasma-assisted molecular beam epitaxy. Structural properties were measured by X-ray diffraction measurement and transmission electron microscopy. XRD spectrum showed the sputtering buffer layer which was mainly (100)$_{AlN}$ and followed by the GaN epilayer which contained poly \textbf{\textit{M}}-plane GaN and other structural planes such as (002)$_{GaN}$ (\textbf{\textit{c}}-plane), and (101)$_{GaN}$. In TEM analysis, we demonstrated GaN of \textbf{\textit{c}}- and \textbf{\textit{A}}-plane grains. The pure \textbf{\textit{M}}-plane GaN was also found in the form of grain and the high-resolution images showed clear atomic arrangement. Besides, the diffraction pattern with multi \textbf{\textit{M}}-plane GaN was attributed to several \textbf{\textit{M}}-plane GaN crystals which were grown in different orientations on in-plane surface. In addition, optical properties measured by photoluminescence and cathodoluminescence measurement both showed two main peaks at 3.2 eV and 3.4 eV, indicated that zinc-blende and wurtzite structure exist in the GaN layer at the same time.