  The electronic structure for a strained Si/SiGe quantum well grown on a
tilted substrate with periodic steps is calculated using a parameterized
tight-binding method. For a zero tilt angle the energy difference between the
two lowest minima of the conduction band at the center of the Brillouin zone
defines a non-zero valley splitting. At finite tilt angles, the two lowest
conduction band minima shift to k0 and -k0 in the Brillouin zone and have equal
energy. The valley splitting for quantum wells grown on a tilted substrate is
therefore equal to zero, which is a direct consequence of the periodicity of
the steps at the interfaces between the quantum well and the buffer materials.
