Quantum Dots and Their Potential Applications to Device Fabrication

Abstract

Size dependent low dimensional semiconductors can be assembled with the optimum quantum efficiency with the desirable properties for fabricating novel optical nano-devices. As a result, the enhancement of electronic and optical properties is observed when the geometrical dimensions are reduced. Optical transitions occurring between confined quantum states or bound to continuum states either in the valence band or in the conduction band or between them are specific of quantum semiconductor structures. The operating wavelength of interband optical devices is dependent on the band gap of a semiconductor on contrary the intraband optical devices exhibit the possibilities of wavelength controlling by design because it involves the transition energy between the levels either in the conduction band or in the valence band. In addition, the quantum confinement of the carriers enhances the interaction between energy levels leading to optical transitions with a narrow bandwidth. The applications of external perturbations and the geometrical confinement induce significant modifications in the electronic and optical properties of a quantum dot. Thus, the reduced dimensionality systems exhibit the novel properties with the superior performance in nano-optical devices including optical amplifiers, high-speed electro-optical modulators, inter-subband long wavelength photo-detectors, diodes, lasers and long wavelength fibre optical communication networks.