Research On Novel Hot-electron Photodetection Based On Surface Plasmon Polaritons And Optical Tamm States

The micro-nano structured photodetectors have the advantages of the ultra-small size, highly compact integration, fast response, and low power consumption, and therefore enable a broad range of applications. Being limited by the material band-structure, the conventional semiconductor photodetectors can normally detect the light with energy beyond the semiconductor band edge. Nevertheless, the hot-electron photodetectors based on surface plasmons(SPs) can overcome this limitation, since the SP resonance can be readily tuned by controlling the structure configuration. Hot-electron photodetection is a new strategy of to detect photo energy, which is based on the process that the hot electrons are excited in the structured metal layer and tunnel through the metal/insulator barrier for photocurrent generation. There have been several great progresses in both theory and experiment in recent years. However, for the newly-emerging field, there is still much room which requires further investigations, including the generation and transport mechanisms of hot electron and the corresponding novel device designs.In this thesis, we investigate the multi-layered hot-electron photodetectors based on metal-insulator(or undoped semiconductor)-metal structures, i.e., MIM or MSM. We focus especially on the fundamental operation principles and mechanisms of the photodetectors, including the electromagnetic response, hot-electron excitation progress, resonance tuning, intrinsic electron transportation, electron collection and optoelectronic optimization, in order to obtain the highly efficient photoconversion, narrow band, angular insensitivity hot-electron photodetector designs.The main works in this thesis are listed as follows:(1) A grating-based photodetector operating at the optical communication window is proposed with a comprehensive study on both the operation principles and the corresponding optimal designs of the plasmonic hot-electron photodetectors. In order to obtain high optical absorption at the wavelength of 1550 nm, the period, width and height of the grating and the thickness of the bottom metal layer are carefully designed in order to control the SP resonance. Further, the analytical and numerical analyses are conducted to mimic the hot-electron transport process inside the MIM structure, to examine the electrical performance of the device. Finally, balancing the optical absorption and electrical response, the system is optimally designed in both the optical and electrical domains so that a high photoconversion response(up to 0.1mA/W without bias) can be obtained.(2) A conformal MSM grating plasmonic hot-electron photodetector is presented and the optoelectronic response is examined. The design enables a strong and highly asymmetrical optical absorption with a high resonant tunability. This is because the absorptions of top and bottom metal layers can be well separated, yielding a nearly perfect optical absorption as well as a high photocurrent. Compared with the conventional grating hot-electron photodetection systems, the conformal design can achieve a net optical absorption over 98%(38% for conventional grating systems). Correspondingly, the hot-electron transportation inside the conformal grating structure is simulated. The electrical simulation predicts that the unbiased responsivity of the conformal device is about 3 times of that based on the conventional grating design.(3) Unlike the traditional hot-electron photodetection systems based on SPs, the optical Tamm states(OTS) is introduced into the hot-electron photodetectors so that an OTS-based planar hot-electron photodetector is presented, which is much simplified in system configuration for the ease of fabrication. Firstly, the underlying physics and controlling strategies of OTS in the system, consisted of the thin metal film and the distributed Bragg reflector(DBR), are studied. Further, the MSM hot electron photodetection components are introduced into the OTS system and corresponding optical performance is examined. Finally, the photocurrent output and the photoresponsivity of the system are quantitatively analyzed by simulating the detailed hot-electron transportation inside the device. Results show that, although the system configuration of the multi-layered planar hot electron photodetector is greatly simplified due to the use of OTS effect, a good photoconversion performance analogous to the traditional micro-nano systems can still be obtained. It provides a new design strategy for low cost and high performance hot electron photodetectors.