  We report on study of low-energy excitations in a bilayer hetero-structure 2D
electron gas. We split the bilayer Hamiltonian into SU(4)-symmetric part and
the anisotropy part and treat the latter as a perturbation. We find that both
Goldstone and the charged excitations - skyrmions - are goverened by the
non-linear Sigma Model. We calculate the anisotropic energy gap of the skyrmion
to have a prominent minimum in the canted antiferromagnetic phase of bilayer.
We compare our findings with the results of recent experiments.
