Localised states in defective CdTe/CdZnTe multi-quantum wells

Abstract

ABSTRACT The current paper presents a theoretical study of the transmission rate and band structure for a multi-quantum wells (MQWs) composed of periodic arrangement of barrier () and well () materials, containing a defect barrier layer. The theoretical calculations of this study are based on the transfer matrix method (TMM) formalism. First, we consider a barrier of thickness d 1 bounded by two semi-infinite substrates. This barrier has its Eigen states with both a high transmission rate and a low quality factor. Then, we take the perfect MQWs system (without defect), whose structure exhibits passbands separated by electronic band gaps (EBGs). These EBGs move towards high energies when the Zn concentration in the barrier increases. Hence the proposed system, behaves like an electronic mirror able to control and manipulate the transfer of electrons by modifying the concentration of the barrier. On the other hand, the insertion of barrier defect induces localised states located in the band gaps, which depends clearly on the concentration (x 0) and the thickness (d 0) of the barrier defect layer made of material. These induced localised states shift to lower energies when increasing the defect thickness. Due to the symmetry of our system, the transmission rates of these localised states reach maximum values and very high quality factors when the defect layer is placed in the middle of the structure. This finding is useful for applications such as light-emitting diodes, semiconductor micro-lasers or in infrared radiation detectors.