The theory of electronic and optical properties of (Si)(n)/(Ge)(m) sup
erlattices (SLSs), within the framework of the tight-binding approxima
tion, is presented. Results for the hand structure, the refractive ind
ex, and the absorption coefficient are given. The important role of in
terface intermixing is studied. Finally a comparative study between th
e properties of Si/Ge SLSs and the corresponding alloys is presented.