Optical characterization of intersubband transitions in Zn _xCd _1-xSe/Zn _x′Cd _y′Mg _{1- x′- y′}Se multiple quantum well structures by contactless electroreflectance

Contactless electroreflectance was measured at room temperature to characterize a wide range of the possible optical transitions in Znx Cd1-x Se Zn x′ Cd y′ Mg1- x′ - y′ Se multi-quantum-well structures grown by molecular beam epitaxy. Based on these measurements, the authors predict and then verify the anticipated intersubband transition energies. They investigate a representative Zn0.5 Cd0.5 Se Zn0.20 Cd0.19 Mg0.61 Se structure, for which the E1-E2 transition energy is predicted to be 178 meV (6.97 μm). Intersubband absorption using Fourier transform infrared spectroscopy exhibits a peak at 180 meV (6.89 μm), in excellent agreement with the contactless electroreflectance measurements.