Homogeneous epitaxial growth of AlN single-crystalline films on 2 inch-diameter Si (111) substrates by pulsed laser deposition

Homogeneous and crack-free AlN films have been epitaxially grown on 2 inch Si (111) substrates by pulsed laser deposition (PLD). By optimising the laser rastering and PLD growth conditions, the 2 inch-diameter single-crystalline AlN films exhibit excellent thickness uniformity with a root-mean-square (RMS) inhomogeneity of less than 3.6% and a very smooth surface with a RMS roughness of 1.4 nm. There is a 1.5 nm-thick interfacial layer between the as-grown AlN films and Si substrates, which is confirmed by HRTEM and a GIXR simulation, and the as-grown AlN films are almost fully relaxed with only 0.3% in-plane tensile strain. The achievement of high-quality and crack-free AlN films with a uniform thickness and abrupt interface on 2 inch Si (111) substrates is of great interest for AlN-based devices, particularly acoustic filters, where abrupt heterointerfaces with the substrates and flat surfaces of AlN films are highly desired.