Research On Photodetector Equivalent Circuit Model And Experiment

Photodetector is the core component of optoelectronic technology, which establishes the relation between optical information and electrical signal and plays a significant role in life, research and military. Therefore, the research on the photodetector is attracting more and more attention. However, as the conventional simulation software has no optoelectronic devices model and can’t analysis the photodetector features quantitatively; the simulation of TCAD software’s use involves lots of optoelectronic device structure and process parameters, which limits its application. This paper established the equivalent circuit models of the PIN photodiode, at the same time, the simulation analysis and experiments were done to describe the model’s feasibility and photodiode features.Firstly, the photodetector operational principle and structure characteristics were discussed. Then, based on carrier rate equation, bipolar transport and boundary condition, according to the equivalent transformation and global parameter, a new PIN photodiode equivalent circuit was established, which included the parasitic parameters and dark current. The equivalent circuit model of PIN photodiode was established in the PSpice software. Based on the model, the PIN photodiode’s I-V characteristic, pulse signal response and dark current were simulated, and the PIN photodiode’s key parameters, such as intrinsic width, composite rate, parasitic capacitance and parasitic resistance were simulated within the time domain and frequency domain, the model feasibility was verified. Then PN photodiode, APD photodiode and photoconductor’s equivalent circuit model were established with the similar way. In addition, consider ing the mechanism of photocurrent, each region’s photocurrent of the PN photodiode component was calculated and added, thus another way to establish the equivalent circuit model was introduced.As the experiments, the infrared pulsed laser diode driver circuit was designed, the influence of external parameters on the output of the laser pulse width and peak were measured. With this pulse laser, the pros and cons of the PIN photodiode was analyzed compared with a professional photodetector. Then the relationship between the photocurrent with external parameters, such as reverse voltage, light intensity, the pulse laser’s width and saturation effects, were studied and the output photocurrent characteristics were discussed.