Intersubband resonant enhancement of second order-nonlinear susceptibility in asymmetric AlxGa1−xN/GaN double quantum wells

Abstract

The present work aims at investigating the second-harmonic generation theoretically in asymmetric AlxGa1−xN/GaN double quantum wells based on a compact density-matrix formalism and a self-consistent approach. Calculations have been made using two- and three-level quantum well models. For this purpose, the electronic subbands and their related wave functions as well as the Fermi energy are computed in asymmetric AlxGa1−xN/GaN double quantum well heterostructures within the effective mass and Hartree approximations. From the given results, it was concluded as follows: (i) The susceptibility exhibits multiple peak structures originating from the intersubband and their corresponding virtual transitions. (ii) The second-order susceptibility strongly depends on the aluminum composition and on the planar-doping design in the barriers as well. (iii) The optimization of electron wave functions' overlaps considerably improved the second-harmonic generation. (iv) Double quantum well systems are revealed to be the most appropriate to generate the second harmonic with an efficient intensity at the suitable resonance frequency. Theoretically, the obtained results would make a useful contribution for experimental studies. From an applied viewpoint, they can open up new opportunities for AlxGa1−xN/GaN optoelectronic devices.