  In this paper, we study a singular perturbation of a problem used in
dimension two to model graphene or in dimension three to describe the quark
confinement phenomenon in hadrons. The operators we consider are of the form $H
+ M\beta V (x)$, where $H$ is the free Dirac operator, $\beta$ is a constant
matrix, $V (x)$ is a real valued piecewise constant potential having a jump
discontinuity across a smooth interface and $M$ is the mass that we can see as
a coupling constant. In particular, we perform a complete asymptotic expansion
of spectral quantities as the mass $M$ tends to $+\infty$.
