  This paper shows the simulation and test results of 50um thick Low Gain
Avalanche Detectors (LGAD) sensors designed by the Institute of High Energy
Physics (IHEP) and fabricated by the Institute of Microelectronics of the
Chinese Academy of Sciences (IME). Three wafers have been produced with four
different gain layer implant doses each. Different production processes,
including variation in the n++ layer implant energy and carbon co-implantation
were used. Test results show that the IHEP-IME sensors with the higher dose of
gain layer have lower breakdown voltages and higher gain layer voltages from
capacitance-voltage properties, which are consistent with the TCAD simulation.
Beta test results show that the time resolution of IHEP-IME sensors is better
than 35ps when operated at high voltage and the collected charges of IHEP-IME
sensors are larger than 15fC before irradiation, which fulfill the required
specifications of sensors before irradiations for the ATLAS HGTD project.
