Research On High Speed Uni-Traveling-Carrier Photodiode (UTC-PD) And Simulation Design Of Transmission Line In Device Packaging

The optical-fiber communication system operating at 100Gbit/s is recently considered to be an ideal candidate as the next generation communication system. High speed photodetectors (PDs) as key components for the the optical-fiber commubication system has become a research focus at domestic and international. The uni-traveling-carrier photodiode (UTC-PD) is a high-speed and high-saturation output photodiode which utilizes only electrons as its active carriers. The main content of this work is to focus on high-speed UTC-PD and high frequency device packaging. The research findings are as follows:1. The model of back-illuminated UTC-PD has been established, and a detailed analysis on the microscopic properties of the device such as energy band, the electric field distribution, carrier density and current density have been given. From the view of earrier transport, the principal of the device and the mechanism of various features generated during the operation are deeply investigated.2. A novel method to improve the high speed performance for UTC-PD by utilizing Gaussian doping to introduce an electric field in the absorption region is proposed. Simulation results showed that the f3dB of UTC-PD with Gaussian doping in the absorption layer is 79GHz, and is 1.9 times higher than that of UTC-PD with the constant doping. When the parameters of the Gaussian doping are selected appropriately, the absorption layer can be divided into a heavy doping region and a lightly doping region. The lightly doping InGaAs region not only acts as absorption, but also acts as a depleted collection layer to help collecting carriers, which results in an increase in responsivity to some extend.3. Research on the theory of transmission line used in the device packaging of optical detector has been made. A Y-shaped conductor-backed coplanar waveguide (CBCPW) differential pair has been designed, which is used for the transmission of high-frequency differential output signal of the MAX3864 chip in the packaging of lOGbit/s optical receiver.4. The packaging model of photodetector has been established. A Taper-shaped GSG pad for the photodetector chip has been designed and a comparison with the round GSG pad has been made. Simulation results showed that the 3dB bandwidth of Taper-shaped GSG pad is 175GHz while that of the round GSG pad is 100GHz. In addition, the model of the CBCPW with vias used to connect the PD chip to a coaxial connector and that of the wire-bonding transitions between the PD chip and CBCPW are established, and the simulation results indicated that the 3dB bandwidth of the connected model is mainly limited by the CBCPW with vias.