Einfluß elektrischer Felder auf die Eigenabsorptionskante fester Körper

This paper realizes an idea ofRedfield in a general and quantitative manner: Charged point defects produce local electric fields in a crystal which cause a change in the absorption-constant compared with the absorption-constant of an undisturbed crystal (Franz-Keldysh-effect). Thus one gets a tail in the absorption constant decreasing from the ideal intrinsic absorption edge towards longer wave-lengths. Applying an external fieldF one finds an additional, frequency-dependent absorptionconstantΔα. Its magnitude and spectral distribution depend on the concentration of defects. For external fields smaller than the internal onesΔα∝ F ² holds at all frequencies. The results are compared with those found byFranz.