Passive electrical model of silicon photomultipliers

An electrical model is developed to simulate, characterize, and predict the response of SSPM detectors for different device geometries and measurement circuit configurations. In particular, the model allows investigation of the effects of increasing parasitic capacitance with increasing diode area on the timing and magnitude of the readout signal. Passive components in the model are extracted from measurements and then used in the model to understand and predict device performance. The avalanche is represented with a switch in series with a voltage source and diode resistor, instead of a current source. This approach allows the change in potential, current through the diode, and timing of the avalanche to be simulated. Experimental and modeled pulses are compared for two different size devices. The model is first developed and validated using the 1×1 mm² device. Predictive capability is demonstrated with the 3×3 mm² device; in the scaling-up of the devices, only expected model parameters are changed, and the experimental and modeled pulses are in good agreement. The current through the diode and voltage change across the diode as functions of time agree with expectations.