Studies On Long-Wavelength Integrated Photodetector And Its Micro Structures Fabrication Technologies For WDM Demultiplexing Receiving Application

With the increasing demand for the bandwidth of the communication, the wavelength-division multiplex (WDM) technology, which is the promising technology to meet the rapid development of the optical communication, has been extensively studied in recent years. Demultiplexing integrated photodetectors with micro-sturctures, as the key device of the WDM system, are the powerful guarantee for the rapid development of the optical communication technology because of the wavelength-selective detection, high-speed, and high compact.In this dissertation, long-wavelength integrated photodetector and its micro-sturctures fabrication technologies for WDM demultiplexing receiving application were studied. Both theoretically and experimentally, the photodetectors with flat-top steep-edge spectral response were studied. The main contents and innovations are listed as follows.1. The Si-based multi-cavity thin film filter was studied. On the theory design, the transmission spectrum of the filters based on different cavity structures were simulated. A novel thin film fiter with flat-top steep-edge spectral characteristics was fabricated successfully. The peak transmittance of75%around1550nm, the-0.5dB band of0.48nm, the3dB band of0.52nm, the25dB band of0.87nm are simultaneously obtained, which can be applied to100GHz channel spacing Wavelength Division Multiplexing systems.2. The BCB low temperature bonding process has been studied. On this basis, a novel Si-based photodetector with good flat-top steep-edge spectral response was proposed. The structure of the photodetector is optimized by theoretical simulation. The photodetector is fabricated by bonding a Si-based multi-cavity F-P filter with an InP-based PIN absorbing structure. A peak quantum efficiency of55%around1550nm, the-0.5dB band of0.43nm,3dB band of0.5nm, the25dB band of1.06nm, and3-dB bandwidth more than16GHz, were simultaneously obtained.3. The step micro-structure, the vertical taper micro-structure, the cone micro-structure were prepared by the innovation of the preparation process. The step micro-structure was realized in the Fabry-Perot filter by the wet etching technology. The vertical taper micro-structure was realized in the absorbing cavity of the photodetector by dynamic mask technology, and the cone micro-structure was realized by the improvation of the dynamic mask technology.4. It’s the first time that a Si-based RCE photodetector with flat-top steep-edge spectral response was fabricated. The photodetector is fabricated by bonding a Si-based multi-cavity F-P filter with an InP-based vertical taper absorbing structure. An integrated device with a peak quantum efficiency of58.42%around1550nm is obtained, which is realized by vertical taper micro-structure. In addition, this photodetector has good performance in the flat-top and steep-edge spectral response, which is realized by the multi-cavity filter. The spectral linewidth is less than0.65nm. The passband flatness is less than0.55dB. The-0.5dB band is0.52nm, and the25dB band is0.95nm.5. A novel wavelength selective photodetector based on a conical absorbing structure has been proposed and fabricated. The preparation process of the cone mirror structure is studied. The base angle of the conical structures can be controlled by changing the depth of the conical forming layer and the radius of the conical mask layer. The top mirror of the absorption cavity was designed to be conical, which can increase the times of light reflection, so the quantum efficiency was improved. An integrated device with a peak quantum efficiency of58.42%around1550 nm is obtained. In addition, this photodetector has good performance in the flat-top and steep-edge spectral response, which is realized by the multi-cavity filter. The spectral linewidth is less than0.7nm. The passband flatness is less than0.55dB. The-0.5dB band is0.5nm, and the25dB band is1.06nm, which can be applied to100GHz channel spacing Wavelength Division Multiplexing systems.6. A monolithically integrated tunable photodetector with flat-top steep-edge spectral response was fabricated. The photodetector is based on GaAs Fabry-Perot filter and an InP PIN. The step structure in the Fabry-Perot filter is realized by wet etching technique, and the high quliaty GaAs/InP heteroepitaxy is realized by employing a thin low temperature buffer layer. By employing a step structure in the filter, this photodetector with flat-top and steep-edge spectral response is fabricated. A peak quantum efficiency of25%around1550nm, the-0.5dB band of3.9nm,3dB band of4.2nm, and3dB bandwidth more than17GHz, were simultaneously obtained.7. The upgrade of software and hardware for the JGP450A9magnectron sputtering system was finished, and the system can achieve fully automatic control.8. The influence of the Au film thickness on the GaAs nanowire growth was studied. By prolonging the deposition time, the thickness of the Au thin film increased, the average diameter of the GaAs nanowires increased, and the growth rate decreased. And, the influence of the working gas pressure on the deposition rate in magnetron sputtering was studied. When the working pressure was0.32Pa, the average deposition rate reached the maximum value, and the best density of metal electrode films could be obtained.