Effect of Al substrate nitridation on the properties of AlN films grown by pulsed laser deposition and its mechanism

AlN films have been grown on nitrided and non-nitrided Al substrates by pulsed laser deposition (PLD) technology at 450 °С. The surface morphology, crystalline quality, and interfacial property of the as-grown AlN films on nitrided and non-nitrided Al substrates have been investigated systematically. It is found that the as-grown ∼300 nm-thick AlN films on nitrided Al substrates show the very smooth surface with a root-mean-square (RMS) surface roughness of 1.5 nm, high crystalline quality with full-width at half-maximum (FWHM) values for AlN(0 0 0 2) and AlN(1 0 −1 2) X-ray rocking curves (XRCs) of 0.6° and 0.9°, and sharp and abrupt interfaces. These results are in striking contrast to those of ∼300 nm-thick AlN films grown on non-nitrided Al substrates. The as-grown ∼300 nm-thick AlN films on non-nitrided Al substrates show relatively rough surface with a RMS surface roughness of 4.0 nm, poor crystalline quality with FWHM values for AlN(0 0 0 2) and AlN(1 0 −1 2) XRCs of 1.1° and 1.5°, and a ∼1.5 nm-thick interfacial layer. Based on the characterizations, the effect of Al substrates nitridation and the growth mechanism of AlN films grown on nitrided Al substrates by PLD are hence proposed. This work provides an effective approach for the growth of high-quality AlN films on Al substrates for the future application of AlN-based devices.