  We study electron dynamics in a two-band delta-doped semiconductor within the
envelope-function approximation. Using a simple parametrization of the
confining potential arising from the ionized donors in the delta-doping layer,
we are able to find exact solutions of the Dirac-type equation describing the
coupling of host bands. As an application we then consider Si delta-doped GaAs.
In particular we find that the ground subband energy scales as a power law of
the Si concentration per unit area in a wide range of doping levels. In
addition, the coupling of host bands leads to a depression of the subband
energy due to nonparabolicity effects.
