Theoretical Research And Experimental Fabrication Of SAGCM-APD

The research work of this thesis was supported by grants from the National Basic Research Program of China (No.2010CB327600),the National High Technology Research and Development Program of China (No.2007AA03Z418) and Program for Changjiang Scholars and Innovative Research Team in University (No.IRT0609)In the optical communication field, firstly the photoreceiver converts optical signals to electrical signals (demodulation). This process can be achieved by avalanche photodiode (APD). APDs are the high-sensitivity detectors utilizing avalanche multiplication effect and are widely used in high-speed optical communications, signal processing, measurement and sensing systems.The detailed theoretical analysis and structure parameters design of SAGCM APD(Separated Absorption, Grading, Charge, and Multiplication Avalanche Photo Diode) were carried out and the InP-based SAGCM APD were experimentally fabricated with its performance tested. The main achievements in this paper are listed as follows.1. The frequency response of SAGCM-APD is detailedly investigated: The frequency response expressions of the InGaAs/InGaAsP/InP and InGaAs/InGaAsP/Si SAGCM-APD are separately derived according to algorithm of multiple spatially uniform layers.The frequency response of SAGCM-APD devices is calculated from the response of each layer using matrix algebra. The assumption that all multiplication takes place at the same plane near the peak electric field has been eliminated. Therefore, the avalanche process is more precisely described and the quantities such as gain and avalanche buildup time are inherently taken into account.2. The impacts of structure parameters of the InGaAs/InGaAsP/InP SAGCM-APD on the characteristics of gain, electric field and frequency response were discussed. The structure parameters are adjusted to achieve the performance requirements according to the required performance parameters, A InP-based SAGCM-APD operating up to 10Gb/s is designed with Wm=0.2μm, Nm=1×1015cm-3 for the multiplication layer, Wc=50nm, Nc=5×1017cm-3 for the charge layer, Wg=80nm, Ng=9×1016cm-3 for the grading layer, Wa=1μm, Na=1×1015cm-3 for the absorption layer. When operated at 90% of the breakdown voltage(32.055V), the APD shows the multiplication gain is 9.757, the 3dB bandwidth is 10.07 GHz and the gain-bandwidth product is 98GHz.3. The InP-based SAGCM-APD devices were experimentally fabricated with the area of 130μm×130μm. The photocurrent and dark current are measured and the testing results were analyzed.