MoS2-assisted growth of highly-oriented AlN thin films by low-temperature van der Waals epitaxy

Abstract

Aluminum nitride (AlN) is a wide bandgap material used in acoustic devices, piezo- micro-electromechanical system and is promising for other electronic applications. However, for most applications, the AlN crystalline quality obtained by PVD or MOCVD is insufficient, and suitable growth substrates providing an adapted lattice match and coefficient of thermal expansion are limited. Alternatively, monocrystalline AlN wafers are not yet available in 200/300 mm sizes and suffer from high costs and quality issues. Here, we propose a novel approach involving a two-dimensional transition metal dichalcogenide (TMD) material as a seed layer, which displays an excellent lattice matching with AlN (>98%) allowing a strong enhancement in the c axis texture of sputtered AlN layers on Si(100)/SiO2 thermal oxide (500 nm) substrates. We have successfully demonstrated an eightfold improvement of the AlN (002) rocking curve compared to reference samples grown on thermal SiO2, thus providing a relevant and cost-effective process for the large-scale deployment of high-quality III-N materials on silicon-based substrates.