Preparation of AlN-Al₂O₃ Composite Films by Microwave Plasma Chemical Vapor Deposition

AlN-Al 2 O 3 composite films were prepared by microwave plasma chemical vapor deposition using an AlBr 3 -H 2 -N 2 -N 2 O-Ar gas mixture on a Si substrate. They were examined with respect to their deposition rate, microstructure, compositions, and refractive indices. Four crystallinity phase regions were observed by X- ray diffractometer as a function of N 2 O gas flow rate and substrate temperature: A, c -axis oriented AlN; B, lower-oriented AlN; C, amorphous; and D, amorphous +β-NH 4 Br. Composite films composed of AlN and Al 2 O 3 microcrystals having an average grain size of 50 nm were detected by transmission electron microscopy observation. Refractive indices, optical band gaps, and surface roughness were also determined.