Hydrogen diffusion, complex formation, and dissociation in acceptor-doped silicon carbide

The diffusion of deuterium (²H) in B and Al doped $4H$ and $6H$ silicon carbide (SiC) has been studied in detail by secondary ion mass spectrometry. From ²H depth profiles, following trap limited diffusion with negligible complex dissociation, an effective capture radius for the formation of ²H-B complexes (at 460 ^∘{}C) is determined to RHB=(21±4). This value is in good agreement with that expected for a Coulomb force assisted trapping mechanism. At annealing conditions where dissociation is non-negligible, the ²H diffusion follows Fick's law with a constant effective diffusivity, from which the complex dissociation frequencies {ν} are determined. The extracted values of {ν} cover three orders of magnitude and exhibit a close to perfect Arrhenius temperature dependence for both ²H-B and ²H-Al complexes. The large difference between the extracted complex dissociation energies, EdHB=(2.51±0.04)eV and EdHAl=(1.61±0.02)eV, suggests that the atomic configurations of the two complexes are significantly different. The corresponding extracted dissociation attempt frequencies, ν₀HB=(1.2±0.7)×10¹³s^-1 and ν₀HAl=(0.7±0.3)×10¹³s^-1, are very close to the characteristic oscillation frequency of the SiC lattice, νlatticeSiC=1.6×10¹³s^-1. This is strong evidence for the assumption of a first order dissociation process. No difference between $4H$- and 6H-SiC has been observed.