High quality factor multichannel filter of electrons based on defective CdMnTe/CdTe multi-quantum wells

Abstract

Using the transfer matrix (TM) method, the propagation of electrons is studied, in a one-dimensional multi-quantum well composed of alternating layers of barriers and wells. In the first time, we proposed system with a single barrier CdMnTe is embedded between two semi-infinite substrates. Hence, the corresponding Eigen modes energies were found to be shifted towards lower energies as the barrier thickness increases. The resulting Eigen modes are characterized by a high transmission rates but a very low quality factor values, which highlight the importance of the system periodicity. On the other hand, in order to create localized states in the band gaps, a defective system is exanimated. Indeed, a defect barrier is inserted in a perfect multi-quantum wells (MQWs) system, basically made of repeated CdMnTe barriers and CdTe wells. This defective system can create multi defect modes in the electronic band gaps. The analysis of the transmittance spectra of the defect states evidences a shift to lower energies by increasing the defect thickness with fixed parameters of the system. These defect states move toward higher energy regions, when the concentration of defect increases. In addition, the energy of the defect states varying from 600 meV to 785 meV. We found one defect state for a defect concentration equal to 0.7, when the defect thickness is equal to 5 A°. Otherwise, for a defect concentration equal to 0.1, with a defect thickness of 150 A°, we found two defect states appeared inside the gaps. While, three defect states were found for a concentration interval between 0.3 and 0.5 and a defect thickness equal respectively to 127 A° and 145 A°. These defect states have higher quality factors reaching 7630000. Moreover, it shown that the number of gaps modes depends on the defect concentration’s and thickness’ parameters. High quality factors are reached, and an electron multi-channel filtering system is then proposed.