Franz-Keldysh effect

The Franz-Keldysh effect describes how an electric field influences a semiconductor's ability to absorb light. When a strong electric field is applied to a semiconductor, it alters the energy landscape of electrons and holes, creating a tail in the absorption spectrum that extends into the energy gap where normally absorption would be minimal. This results in enhanced light absorption at certain energies and causes shifts in how the material interacts with light, especially near the material's band edge. The effect is important in designing devices like modulators and detectors in optoelectronics.