Polytype pure sp2-BN thin films as dictated by the substrate crystal structure

Chubarov, M. and Pedersen, H. and Högberg, H. and Czigány, Zsolt and Garbrecht, M. (2015) Polytype pure sp2-BN thin films as dictated by the substrate crystal structure. CHEMISTRY OF MATERIALS, 27 (5). pp. 1640-1645. ISSN 0897-4756

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Abstract

Boron nitride (BN) is a promising semiconductor material, but its current exploration is hampered by difficulties in growth of single crystalline phase-pure thin films. We compare the growth of sp2-BN by chemical vapor deposition on (0001) 6H-SiC and on (0001) α-Al2O3 substrates with an AlN buffer layer. Polytype-pure rhombohedral BN (r-BN) with a thickness of 200 nm is observed on SiC whereas hexagonal BN (h-BN) nucleates and grows on the AlN buffer layer. For the latter case after a thickness of 4 nm, the h-BN growth is followed by r-BN growth to a total thickness of 200 nm. We find that the polytype of the sp2-BN films is determined by the ordering of Si-C or Al-N atomic pairs in the underlying crystalline structure (SiC or AlN). In the latter case the change from h-BN to r-BN is triggered by stress relaxation. This is important for the development of BN semiconductor device technology.

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