Molecular beam epitaxy and characterization of wurtzite LaAlN
Rui Shen, Md Mehedi Hasan Tanim, Jiangnan Liu, Samuel Yang, Yutong Gan, Yiran Li, Jie Zhang, Hai Nguyen, Xiao Zhang, Emmanouil Kioupakis, Parag Deotare, Mackillo Kira, Kai Sun, Zetian MiWe report the molecular beam epitaxy and structural characterization of single-phase wurtzite LaxAl1−xN thin films, with a La composition as high as x=0.20. In situ reflection high-energy electron diffraction confirms epitaxial film formation, and atomic force microscopy reveals sub-nanometer surface roughness for all compositions investigated. High-resolution x-ray diffraction and scanning transmission electron microscopy further confirm c-axis orientation, high crystalline quality, and precise in-plane epitaxial alignment. Importantly, atomic-resolution structural analysis demonstrates a continuous decrease in the c/a lattice-parameter ratio with increasing La content. In addition, out-of-plane piezoresponse force microscopy measurements show an enhanced effective d33, increasing from 5.00 pm/V for AlN to 7.66 pm/V for La0.20Al0.80N. These results establish LaAlN as a promising new wurtzite nitride alloy platform for future wide bandgap electronics, optoelectronics, and quantum photonics.