A singularly perturbed traveling wave problem derived from the drift d
iffusion model describing electron transport in two-valley semiconduct
or materials is analysed. It is shown that the reduced problem, define
d on a submanifold of the phase space, has homoclinic orbits for certa
in parameters. By using methods from invariant manifold theory and met
hods from homoclinic continuation theory, it is proved that the homocl
inic orbits of the reduced problem persist in a global center manifold
near the manifold of the reduced problem.