Studies of growth processes in silicon carbide epitaxial layers from the vapour phase

Controllable 6H-SiC to 4H-SiC polytype transformation during PVT growth

“…Furthermore, higher growth temperatures decrease the probability of 15R-SiC nucleation [12]; (c) 4H-SiC compared to 6H-polytype requires lower Si/C ratio [13,17,18] of the vapor. Using the high axial gradient permits significant rise of the source temperature; thus, the vapor becomes more carbon rich [17,31]; and (d) formation enthalpy of the 4H-SiC is higher than that of 6H-SiC [17], and hence, the high axial gradient helps in effective removal of the excess of heat of crystallization.…”

“…The vapor stoichiometry coefficient (Si/C ratio) can be calculated as [31] where N Si and N C are the molar fractions of silicon and carbon, respectively; and p Si represents partial pressure of atomic Si at the temperature of sublimation T. The calculated value of the stoichiometry coefficient g theor (2360 1C) ¼ 1.59. In spite of the incongruent sublimation of the source, we did not find evidence of either silicon losses during growth or solid silicon residue in the growth cell.…”

“…In order to estimate the temperature conditions in the growth cell during our actual growth runs, numerical simulations have been employed using FIDAP/GAMBIT software package. Having values of the temperature gradients and source material temperature from the model and actual growth conditions (argon background pressure and temperature at the crystal backside), values of supersaturation and Si/C ratio in the gaseous phase at the growth front were calculated using thermodynamic parameters of SiC evaporation [17,18,31].…”

Fast epitaxy by PVT of SiC in hydrogen atmosphere

“…This suggests that the Si/C ratio at the growth front is decreased by hydrogen since step-bunching in SiC is known to appear at a decreased Si/C ratio [4]. Also, a carbon enrichment in the vapor is supported by calculations related to sublimation growth in hydrogen [3,5].…”

Preferential carbon etching by hydrogen inside hexagonal voids of 6H-SiC(0001)

“…Under equilibrium conditions at an hydrogen pressure of 13 mbar and 1800°C, the pressure of the most important reaction products ͑i.e., Si, C 2 H 2 , CH 4 ) in the gas phase is of the order of 10 Ϫ2 mbar. 9 At this partial pressure, the molecular flux due to the Maxwell distribution of velocities in the gas phase is of the order of 100 molecules/ (Å 2 s). This flux gives the upper limit for diffusion of the reaction products away from the surface and corresponds to a maximum etching rate of the order of 60 m/h.…”