Effect of nitrogen impurity on the stabilization of 3C–SiC polytype during heteroepitaxial growth by vapor–liquid–solid mechanism on 6H–SiC substrates

This work reports on the stabilization of 3C–SiC polytype during heteroepitaxial growth by vapor–liquid–solid (VLS) on on-axis and 2° off-axis 6H–SiC(0001) substrates using Si–Ge as liquid phase. It was found that, depending on growth conditions (mainly temperature or nitrogen amount in the reactor), the deposit could be either a complete 3C or 6H–SiC layer or even a mixture of both polytypes. The proportion of 3C inside the deposit increases when 1) nitrogen amount in the reactor increases or 2) temperature is decreased. Though the effect of temperature could be explained in terms of 3C–SiC initial island dissolution, the influence of nitrogen is less obvious but it is shown to be effective at the early stage of growth. Several hypotheses are proposed such as SiC lattice modification by N incorporation or surface effects during the early stage of growth.

Research Highlights
► 3C-SiC polytype could be stabilized by nitrogen impurity during VLS growth.
► Its presence is only necessary at the nucleation stage of the growth.
► The main source of N impurity is the crucible itself.
► 6H homoepitaxy is obtained when N amount is initially small or at high temperature.
► SiC lattice modification and/or surface effects are proposed to explain the results.