Properties of biexcitons in multi-valley semiconductors

This paper considers the effects on the symmetries and binding energies of biexcitons of 1) the short-range interaction (Coulomb and exchange), 2) a multi-valley conduction band and 3) the mass anisotropy of the valleys. It demonstrates that the ground state of the biexciton in a multi-valley semiconductor should be a spin triplet with an antisymmetric valley function and that poly-excitons X x, x>2, should be stable in a material like Si. © 1977 Società Italiana di Fisica.