  A theory of the circular photogalvanic effect caused by spin splitting in
quantum wells is developed. Direct interband transitions between the hole and
electron size-quantized subbands are considered. The photocurrent excitation
spectrum is shown to depend strongly on the form of the spin-orbit interaction.
In the case of structure inversion asymmetry induced (Rashba) spin-splitting,
the current is a linear function of light frequency near the absorption edge,
and for the higher excitation energy the spectrum changes its sign and has a
minimum. In contrast, when the bulk inversion asymmetry (Dresselhaus splitting)
dominates, the photocurrent edge behavior is parabolic, and then the spectrum
is sign-constant and has a maximum.
