Mid-infrared optical transitions of a hydrogenic impurity in the conduction band of a Cd1 − xZnxSe/ZnSe parabolic quantum dot

Abstract

Theoretical investigations on the absorption spectra for the intersubband optical transitions in a Cd1 − xZnxSe/ZnSe quantum dot are performed. Calculations on the electronic states are investigated using a variational scheme within the single band effective mass approximation and the optical gain is calculated using the compact density matrix approach with the iterative procedure. 2p-1s like transition energy and the spontaneous transition lifetime of the shallow donor hydrogenic impurity with the geometrical confinement and the Zn alloy content in a Cd1 − xZnxSe/ZnSe quantum dot are computed. The optical gain as a function of incident photon energy with the effects of spatial confinement and the Zn composition is found. The results show the dependence of the transition energy on the electron density in the Cd0.8Zn0.2Se/ZnSe quantum dot and the magnitude of the optical absorption coefficient enhances when the electron density increases. It is observed that a 1.55 μm wavelength is achieved for a 22 Å radius of a Cd1 − xZnxSe/ZnSe quantum dot. This band gap tunability brings out the possibility for near-infrared detectors, fiber optical communication systems and absorption modulators.