This is a Retraction for the article 2008 J. Phys. A: Math. Theor. 41 215302.It has come to the attention of IOP Publishing that this article should not have been submitted for publication owing to its substantial replication of an earlier-published paper (Bernardini A E 2008 Delay time computation for relativistic tunneling particles Eur. Phys. J. C 55 125–32) and consequent technical breach of the Editorial Guidelines. Consequently, this paper has been retracted by IOP Publishing.