The Timing Resolution of IHEP-NDL LGAD Sensors With Different Active Layer Thicknesses

The thickness of the high-resistivity layer (active layer) is a crucial factor affecting the timing resolution of low gain avalanche diodes (LGADs). We studied the potential improvement of the timing resolution of charge particles based on LGADs with different active layer thicknesses. The Institute of High Energy Physics (IHEP) and the Novel Device Laboratory (NDL) jointly designed two types of LGAD sensors with active layer thicknesses of 33 and 50 $\mu \text{m}$ . The timing resolution is given by contributions from the time walk, jitter, and nonuniform charge deposition (Landau term). The jitter and the Landau term contributions in the timing resolution are extracted by the combination of the ${^{90}{Sr}}$ beta source test and the picosecond laser test. The Landau contribution is found to be the dominant contribution for both types of LGAD sensors, and the Landau contribution of the 33 $\mu \text{m}$ sensor is lower than that of the 50 $\mu \text{m}$ sensor. Based on the experimental results, we perform the simulation for thinner active layer LGAD with the WeightField2 program. The timing resolution can be further improved by reducing the active layer thickness from 33 to 20 $\mu \text{m}$ .