Vapor-liquid-solid growth of 3C-SiC on α-SiC substrates.: 1.: Growth mechanism

We report on the heteroepitaxial growth of 3C-SiC layers by a vapor-liquid-solid (VLS) mechanism on various alpha-SiC substrates, namely, on- and off-axis for both 4H- and 6H-SiC(0001), Si and C faces. The Si-Ge melts, in which the Si content was varied from 10 to 50 atom%, were fed by 3 sccm of propane. The growth temperature was varied from 1200 to 1600 degrees C. It was found that single domain 3C-SiC layers can be obtained on 6H-SiC off- and on-axis and 4H-SiC on-axis, while the other types of substrates gave twinned 3C-SiC materials. As a general rule, one has to increase temperature when decreasing the Si content of the melt to avoid twin formation. It was also found that twinned 3C-SiC layers form at low temperatures, while homoepitaxy is achieved at high temperatures. Some growth mechanisms are proposed to explain the possibility of achieving either homoepitaxial or 3C-SiC layers (twinned or twin free) by changing the growth conditions. Concerning the selection of one orientation of the 3C layer for twin elimination, correlation with the carbon solubility in the melt and surface characteristics of the alpha-SiC seed are discussed.