Design and simulation of silicon photo-multiplier

Abstract

Silicon Photo-Multiplier (SiPM) is a state of the art photo-detector, capable of detecting extremely low light flux as low as single photon with high gain (∼ 105) and high resolution. The SiPM consists of a large array of Avalanche Photo Diodes (APDs), connected to a common grid through individual series resistors and biased in ‘Geiger’ mode. Due to various advantages of SiPM such as high quantum efficiency, smaller footprint and smaller size it has been sought after as replacement for conventional Photo Multiplier Tubes. Thus, SiPM is being widely used in many high energy experiments such as CMS experiment at CERN. We have proposed indigenous design for the SiPM, designed and optimized through extensive TCAD simulations. The APD structure was optimized at the wavelength around 490 nm making it suitable for various high energy experiments like GRAPES-3 in India. Various characteristics of the device were studied such as I-V and C-V characteristics, spectral response of the device and transient response. Implanted guard rings were designed resulting in significantly reduced electric field near edges (∼ 40000 V/cm) compared to its value of 4×105 V/cm at the main junction. This has ensured lower leakage currents and no edge breakdown of the device. Fabrication process for the proposed device was designed with local foundry parameters enabling more realistic design.