Research On Photon Manipulation And Photovoltaic Effect In Micro And Nano Photonic Structures

Recently, with the rapid development of the micro and nano fabrications, micro and nano semiconductor structures (such as photonic crystals, quantum dot, quantum well, nano wires, etc) have been widely used in optoelectronic devices. Electromagnetic theory and quantum physics combine together in micro and nano semiconductor devices, photon manipulations and photovoltaic effect are two important topics in modern optoelectronic devices.The work in this thesis is supported by the National High Technology Research and Development Program of China (Grant No.2009AA03Z405) and the National Natural Science Foundation of China (Grant No.60971068), and focus on the growth of micro and nano semiconductor material, movement of the photons and light-matter interaction in the optoelectronic devices. The FDTD method is used in the calculation of electromagnetic wave movement. This thesis covers the following six main contributions:1. Research on the physical characters in the growth of semiconductor. The growth of the semiconductor materials (eg. GaN film and SiGe superlattice) is important to the optoelectronic devices. Dynamic characters and the physical characters in the process of the growth can be obtained by using Molecular Dynamics method, which is a base of the fabrication of the optical communication and optoelectronic devices.2. Light-matter interaction in quantum dot and new explanation for Stokes shift effect in colloidal QD. By comparing the experiment spectrum and numerical calculation, we found that the optical excitation of an exciton in the QD will couple with the external excitation radiation (i.e., exciton polariton) and affect the dielectric constant of the QD very much, which leads to variations of the optical power inside the QDs, Thus leads to a shift between the light absorption peak and emission peak (i.e., Stokes shift). This is useful in bio-photonics and single-photon communication field.3. Light manipulation in photonic crystal waveguide and its application in free space communication. Utilizing the photonic crystal bandgap character, one-to-two (one beam in and two beams out), one-to-three, and one-to-five beam splittings to free space from a two-dimensional photonic crystal waveguide (PCW) has been realized by adding and modifying a few additional dielectric rods at the exit of the PCW. The split beams have symmetric energy distributions and high directional transmissions. The design is very useful for the free-space-communication devices.4. Photonic crystal structure for light diffraction in Quantum well/dot infrared photodetectors (QWIP/QDIP). Quantum well (QW) and dome-shaped quantum dot (QD) can not absorb the normal incident radiation and favor the Electric field that in the injection direction. In this work, we study two kinds of photonic crystal structures made of metallic and dielectric materials to diffract and couple the normal incident light into the active layers, which enhance the light absorption in QWIP and QDIP.5. Surface Plasmon structure in QWIP and QDIP. Surface Plasmon wave excited by subwavelength hole arrays at metal-semiconductor interface can diffract the electric field in near field region and create useful field component for QWIPs and QDIPs. This can increase the light-matter interaction and photocurrent in QWIP and QDIP.6. Photonic crystal (PhC) in QD or dye solar cells. PhC structures can efficiently diffract incident light from its initial incident direction to other directions in the PhC lattice when the wavelength is out of the bandgap. Further light trapping can be obtained by using comb-shaped PhC structure because comb-shaped PhC structure can create extra resonance modes. We design a comb-shaped PhC framework with CdSe QDs or dye materials immersed in the lattice for high-efficiency solar radiation absorption. The structure not only increases the propagation paths of light in the active region but also creates useful electric field modes in the lattice to trap the light. These will enhance the light-matter interaction.