Research Of Physical Characteristics And Equivalent Circuit Model For High-Gain Photodetector

Photodetector is the main component of the fiber-optic communication systems and photoelectric detection, which has very importment effect. And, avalanche photodetector which with high gain due to its internal gain has become one of the most important works in detector system. The infulenct of thick and doping concentration of avalanche photodetector on electric field distributions, current response, I-V characteristics and time domain response characteristics has been analysed and discussed. Main concludes and results are as follows:The software of APSYS is used to simulate device model of separate absorption, grading, charge and multiplication avalanche photodetector, which due to drift-diffusion theory. Basic physical quantities such as band diagram, optical absorption and generation are calculated. Performance characteristics such as dark-current and photo-current, photoresponsivity, multiplication gain, breakdown voltage are simulated. The result further show that, the better electrical field distribution and current response achieved with higher doping concentration and thinner charge layer width.The current time response of the devices has been simulated, and the trade-off between the bandwidth and the quantum efficiency of the potodetector has been discussed. Besides, the influence of carriers and dead-apace effect on devices charatceristic has been simulatated and discussed due to transfer function. Then, the equivalent circuit model is derived.In order to further increase multiplication gain, the resonant cavity enhanced avalanche photodetector with Fabry-Perot coule generate more free carriers under the conditions of a certain incident, and the electronic field in the devices was changed besacuse of the Fabry-Perot coule.