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

The thickness of the high-resistivity layer (activelayer) is a crucial factor affecting the timing resolution oflow gain avalanche diodes (LGADs). We studied the poten-tial improvement of the timing resolution of charge particlesbased on LGADs with different active layer thicknesses. TheInstitute of High Energy Physics (IHEP) and the Novel DeviceLaboratory (NDL) jointly designed two types of LGAD sensorswith active layer thicknesses of 33 and 50μm. The timingresolution is given by contributions from the time walk, jitter,and nonuniform charge deposition (Landau term). The jitterand the Landau term contributions in the timing resolution areextracted by the combination of the90Srbeta source test andthe picosecond laser test. The Landau contribution is found tobe the dominant contribution for both types of LGAD sensors,and the Landau contribution of the 33μm sensor is lowerthan that of the 50μm sensor. Based on the experimentalresults, we perform the simulation for thinner active layer LGADwith the WeightField2 program. The timing resolution can befurther improved by reducing the active layer thickness from33 to 20μm.