Intersubband Transition And Coherent Tunneling In Coupled Quantum Wells

A detailed theoretical study and calculation of intersubband transition, optical absorption and coherent tunneling processes in double quantum well structures composed of Al0.3Ga0.7As/GaAs are presented, which is based on semiconductor materials and the energy band structure.Firstly, the effect of the electric field and intense laser field on the intersubband transition and optical absorption in anAl0.3Ga0.7As/GaAs asymmetric double quantum well is theoretically investigated by using the transfer matrix approach. The Hartree potential due to the electron-electron interaction is considered in our calculation. For intersubband transitions in an asymmetric double quantum well, it shows that the peaks of the absorption coefficient are found to be a blue or red shifted by tuning the intensity of the laser field and the applied electric field. It can be concluded that the intense laser field and external electric field have a considerable influence on the electronic and optical properties for an asymmetric double quantum well. This gives a new degree of freedom in various device application based on the intersubband transition.The coherent tunnelling and escape tunneling processes through asymmetric coupled quantum wells are investigated by considering an external electric and magnetic field. The transfer matrix approach and finite difference method are used to solve the stationary Shrodinger equation and time-dependent Shrodinger equation respectively. It is found that the electron is fully located in a single well at the case of nonresonance, but the eigenstates are delocalized near the resonance. The magnetic field and barrier thickness plays an important role in modulating the electron states and tunneling time. The lifetime of coherent tunneling are decreased as the transverse magnetic field increasing.