Ab initio-based approach to structural modulation on 4H-SiC(1 1 2¯ 0) during MBE growth

We systematically investigate adsorption behavior of Al and N atoms and resultant atomic arrangements of AlN monolayer on 4H-SiC(1 1 2¯ 0) surfaces using ab initio-based approach. The calculated results for the single Al or N adatom on the 4H-SiC(1 1 2¯ 0) reveal that the stable adsorption site for the Al is near the lattice site of the 4H structure, whereas the N stays at the interstitial site located above top C atom. The N adatom desorbs except the most stable site at the conventional growth temperature ~1200 K. Furthermore, the distinctive atomic arrangements appear when successive adsorption of Al and N atoms after N and Al pre-depositions, respectively. Even after the N deposition, the successive Al adatom occupies the 4H-like lattice site similarly to the results for the single Al on the surface. On the other hand, the N adatom tends to form the dimer structure with the pre-deposited Al. On the basis of these results, the structural modulation of AlN monolayer on the 4H-SiC(1 1 2¯ 0) is discussed performing the electron counting Monte Carlo simulations under Al- and N-rich limits.