Studies On Integrated Photodetector Based On Micro/Nano Structures

With the rapid development of the optical communications and optical computer, the increase in digitalized communication is exponential. Photodetector is a crucial element of modern optical telecommunication systems, so the high-performance photodetector is required. Integrated photodetectors based on micro/nano sturctures are the way of the future because of their high performance, compact and simple manufacture technology.In this dissertation, integrated photodetector based on micro/nano sturctures was studied. The key technologies for fabricating the photodetector were studied. Both theoretically and experimentally, the photodetector based on subwavelength grating and micro-ring waveguide photodetector were studied. The scan electronic microscope (SEM) is modified to be an electron beam lithography system. The electron beam lithography system and nanolithography were studied. The main contents and innovations are listed as follows.1. The subwavelength grating was studied thoroughly and the simulation result has been got. InP subwavelength gratings were designed and fabricated successfully. Ranging from1460nm-1610nm wavelength regimes, InP subwavelength gratings is over67%reflective in experiments, which was a good reflector for InP-based devices.2. SOI subwavelength gratings were designed and fabricated successfully. Line grating and circular grating were studied respectively. Ranging from1460nm-1610nm wavelength regimes, the line gratings is75～94%reflective in experiments. Ranging from1460nm-1610nm wavelength regimes, the circular gratings is over70～80%reflective in experiments.3. A novel subwavelength metal grating is proposed that has a very broad reflection spectrum and very high reflectivity. It consist of Au grating and a thin layer of SiO2, Ranging from1460nm-1610nm wavelength regimes, the circular gratings is over70～80%reflective in simulations.4. The photodetector in which the subwavelength grating was used as the bottom mirror was fabricated successfully. Quantum efficiency was increased by20%because of using the subwavelength grating. To date, there is no report about the photodetector with similar structure which working in communication bands.5. Micro-ring waveguide photodetector was designed and fabricated successfully. The Resonance characteristics of micro-ring waveguide photodetector were obtained by experiment. The photodetector had responsivity of over0.2mA/W for1560nm, with based at0.2V.6. The SEM is modified for electron beam lithography successfully. The principle and process of the electron beam lithography was studied. Nanostructures were fabricated by the electron beam lithography successfully. The smallest feature that can be created by the electron beam lithography system is80nm. The electron beam lithography can been used in many fields such as micro fabrication.