The thermal stability of the passivating hydrogen-aluminum complex ((2)HAl) in 4H-silicon carbide has been studied by determining the effective diffusion constant for hydrogen in an AI-doped epitaxial layer. Assuming a complex comprised of one (2)H and one AI acceptor ion, the extracted diffusivities provide the dissociation frequency of the complex. The extracted frequencies cover three orders of magnitude and yield a close to perfect fit to an Arrhenius equation with the extracted dissociation energy for the (2)HAl-complex equal to 1.66 (+/-0.05) eV and a pre-exponential attempt frequency nu (0) = 1.7x10(13) s(-1) in good agreement with the expected value for a first order dissociation process.