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.