This issue is a well known problem in high energy physics which is called " Neutrino Billiards". You can find a full description about it in:
Berry, M.V. and R.J. Mondragon, Neutrino Billiards: Time-Reversal Symmetry-Breaking Without Magnetic Fields. Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences, 1987. 412(1842): p. 53-74.
And in the case of graphene C.W.J. Beenakker have a good paper about this problem:
Physical Review Letters, 2006. 96(24): p. 246802. or it's Arxiv:0603315 counterpart.
in summary: for making bound states from massless Dirac fermions you must use a mass term in each bound instead of electric potentials. So the probability of Klein tunneling set to zero and fermions became confined.