Absorption tail of low resistivity CdSexTe1-x : comparison between absorption and quantum efficiency measurements

Optical‐absorption and photocurrent spectra of a Schottky junction under different bias are compared for CdSexTe1−x (0.54≤x≤1), near the energy gap, at room temperature. An exponential dependence (Urbach tail) is established for both kinds of spectra; however the logarithmic slope of the photocurrent tail is shown to be larger than that of the absorption. Furthermore, this slope increases with forward bias applied to the Schottky diode. These phenomena can be accounted for by a model that considers light absorption, tunneling, and transport of minority carriers. Satisfactory agreement with experimental results is obtained.