Electronic states in [formula omitted] MQWs induced by two defect layers

Abstract

In this article, we investigate the existence and the behaviour of electronic states located in the band gap of Multi-Quantum Wells (MQWs) disturbed by two layers of defects. The MQWs consist of two periodic semiconductor materials (GaAs/Ga1−xAlxAs/GaAs), and the whole structure is sandwiched between two GaAs substrates of the same nature. We use the formalism of the interface response theory to study the transmission and the variation of energy levels. The creation of defects in the MQWs is carried out either by a local modification of the concentration of aluminium x or by changing the thickness of the layers in the studied structure. In a first study, we insert two geometrical defects inside the perfect MQWs that show a modification in the electronic band structure, which leads to a variation of the energies of the electronics states. Then we perturb the perfect MQWs by two material defects, which modify the barrier heights and the effective masses of the two defects layers. The results show that the position, thickness, and concentration of Al in the two defective layers play a crucial role in increasing electronic states, thus promoting the transfer of electrons without using higher energy. These electronic states are of practical interest for the characterization of the electronic properties of thin-film materials and can be the basis of new electronic and optoelectronic devices.