Quantum confined Stark effect of II-VI heterostructures suitable as modulators in the blue–green spectral region

We present a systematic and quantitative investigation of the quantum confined Stark effect in (Zn, Cd)Se/Zn(S,Se) quantum well structures at room temperature. For this purpose, differential transmission spectroscopy is performed on two samples with different thicknesses of the active layers (4×5 nm and 10 nm) and compared to model calculations. We observe a Stark shift of 18 meV in the heavy-hole exciton peak for an electric-field change from 82 to 175 kV/cm for the 4×5 nm sample. In contrast, the 10 nm sample shows a rather weak and more Franz–Keldysh-like signal. Furthermore, we have analyzed the spectral behavior of the linewidth enhancement factor αH. Values between 5.1 and 0.2 are found at the energy of absolute maximum of the absorption change for the 4×5 nm sample.