  As a new member of GECAM mission, the GECAM-C (also called High Energy Burst
Searcher, HEBS) is a gamma-ray all-sky monitor onboard SATech-01 satellite,
which was launched on July 27th, 2022 to detect gamma-ray transients from 6 keV
to 6 MeV, such as Gamma-Ray Bursts (GRBs), high energy counterpart of
Gravitational Waves (GWs) and Fast Radio Bursts (FRBs), and Soft Gamma-ray
Repeaters (SGRs). Together with GECAM-A and GECAM-B launched in December 2020,
GECAM-C will greatly improve the monitoring coverage, localization, as well as
temporal and spectral measurements of gamma-ray transients. GECAM-C employs 12
SiPM-based Gamma-Ray Detectors (GRDs) to detect gamma-ray transients . In this
paper, we firstly give a brief description of the design of GECAM-C GRDs, and
then focus on the on-ground tests and in-flight performance of GRDs. We also
did the comparison study of the SiPM in-flight performance between GECAM-C and
GECAM-B. The results show GECAM-C GRD works as expected and is ready to make
scientific observations.
