Intersubband Transitions in the Quantum Dot Layers for Quantum Confined Photodetector

In nanostructure like quantum dots (QDs) embedded in the spacing layer with high energy barrier, where electrons are three-dimensionally confined into nanometer-scale semiconductor structures, the novel physical characteristics are expected to emerge. The novel properties would greatly improve semiconductor device performance. Optoelectronic devices with quantum dot heterostructure like quantum dot infrared photodetector (QDIP) have already been proposed in the recent years. When QDs are incorporated into the layered structure of a semiconductor for optoelectronic device applications, electrical control is critical to the operation of device. It is desirable that both an electric field can be applied to change physical properties of the QDs embedded in the spacing layers i.e., the active region of the device and that the photo-induced carriers can be excited and transited to generate the photocurrent. In this chapter, The pseudopotential model of using multiple-quantumdot (MQD) structures for detect infrared radiation can be explained by exploiting the basic principles of quantum mechanics, with the uniform and isotropic strain-induced potential to well simulate the electronic properties of InAs/In(Ga)As QDIP active region by finite element method (FEM). The vertically coupled and decoupled wave-functions of electrons on MQD with dependences of thickness of spacing layers are also calculated by means of the FEM. The method is ideally suited for numerical analysis by computer. The typical and particular QDIP structure are involved and introduced in this section. Here, the outstanding performance of the QDIP which has emerged as a potential alternative to QWIPs would be proposed. The motivation for interest in QDIPs is rooted in two characteristics of quantum dots. The first is that QDIPs are sensitive to normal-incident infrared radiation, a consequence of the 3-D confinement of electrons in the quantum dots. The other attribute is the weak thermionic coupling between the ground state and excited states. This should result in lower thermal excitation and, thus, lower dark current and higher operating temperature. The concomitant increase in the lifetimes of excited carriers should enable higher responsivities as carriers have more time to escape and contribute to the 13