Molecular beam homoepitaxy on bulk AlN enabled by aluminum-assisted surface cleaning
Yong-Jin Cho, Celesta S. Chang, Kevin Lee, Mingli Gong, Kazuki Nomoto, Masato Toita, L. J. Schowalter, David A. Muller, Debdeep Jena, Huili Grace Xing
Abstract
We compare the effectiveness of in situ thermal cleaning with that of Al-assisted cleaning of native surface oxides of bulk AlN for homoepitaxial growth by molecular beam epitaxy. Thermal deoxidation performed at 1450 °C in vacuum results in voids in the AlN substrate. On the other hand, Al-assisted deoxidation at ≈900°C results in high-quality AlN homoepitaxy, evidenced by clean and wide atomic terraces on the surface and no extended defects at the growth interface. This study shows that Al-assisted in situ deoxidation is effective in removing native oxides on AlN, providing a clean surface to enable homoepitaxial growth of AlN and its heterostructures; furthermore, it is more attractive over thermal deoxidation, which needs to be conducted at much higher temperatures due to the strong bonding strength of native oxides on AlN.