Interband multilevel transitions in ZnO/MgZnO asymmetric double quantum wells

Abstract

In this paper, we report a theoretical study on electron interband transitions in ZnO/MgZnO asymmetric double quantum wells under external electric and magnetic fields, using the effective mass approximation to calculate eigenenergies and wave functions of electrons, heavy holes, and light holes. The first-order linear and third-order nonlinear optical absorption coefficients and refractive index changes during multilevel transitions are analyzed in detail, revealing that the optical behavior of the system is significantly modulated by both the electric field (orientation and intensity) and magnetic field (magnitude). Specifically, optical parameters associated with the ground state (E1) and first excited state (E2) of electrons exhibit opposite trends under forward/reverse electric fields: positive fields suppress E1 related transitions (e.g., a 99.73% decrease in the absorption from the heavy hole ground state to the electron ground state) but enhance E2 related transitions, while negative fields show the reverse behavior. Heavy hole transitions dominate the optical response due to their more localized wave functions, outperforming light hole transitions in absorption intensity. Under magnetic fields (up to 20T), quantum confinement is enhanced, leading to slight increases (2.38%–8.33%) in optical absorption peaks for E1-related transitions and decreases ($\sim$28%) for E2-related transitions, though the overall impact is weaker than that of electric fields. These findings provide theoretical insights for optimizing the optoelectronic properties of ZnO-based materials in ultraviolet detectors and optical modulators.