Advances in the molecular-beam epitaxial growth of artificially layered heteropolytypic structures of SiC

The controlled growth of SiC heteropolytypic structures consisting of hexagonal and cubic polytypes has been performed by solid-source molecular-beam epitaxy. On on-axis substrates, 4H/3C/4H-SiC(0001) and 6H/3C/6H-SiC(0001) structures were obtained by first growing the 3C-SiC layer some nanometer thick at lower substrate temperatures (T=1550 K) and Si-rich conditions and a subsequent growth of alpha-SiC on top of the 3C-SiC layer at higher T (1600 K) under more C-rich conditions. On off-axis substrates, multiheterostructures consisting of 4H/3C- or 6H/3C-stacking sequences were also obtained by first nucleating selectively one-dimensional wire-like 3C-SiC on the terraces of well-prepared off-axis alpha-SiC(0001) substrates at low T(< 1500 K). Next, SiC was grown further in a step-flow growth mode at higher T and Si-rich conditions. After the growth, many wire-like regions consisting of 3C-SiC were found also within the hexagonal layer material matrix indicating a simultaneous step-flow growth of both the cubic and the hexagonal SiC material. (C) 2000 American Institute of Physics. [S0003-6951(00)01039-1].