Zener breakdown in the optical absorption of semiconductor superlattices

Electrical breakdown in the optical absorption of strongly coupled superlat tices takes place at high, but realistic electric fields. The Zener breakdo wn is characterized by a strong inhomogeneous line broadening and, eventual ly, the disappearance of sharp transitions. We show that the Zener breakdow n is unambiguously related to the continuous nature of the spectrum and the infinite extension of the wave functions.