  AMIGA (Auger Muons and Infill for the Ground Array) is an upgrade of the
Pierre Auger Observatory designed to extend its energy range of detection and
to directly measure the muon content of the cosmic ray primary particle
showers. The array will be formed by an infill of surface water-Cherenkov
detectors associated with buried scintillation counters employed for muon
counting. Each counter is composed of three scintillation modules, with a 10
m$^2$ detection area per module. In this paper, a new generation of detectors,
replacing the current multi-pixel photomultiplier tube (PMT) with silicon photo
sensors (aka. SiPMs), is proposed. The selection of the new device and its
front-end electronics is explained. A method to calibrate the counting system
that ensures the performance of the detector is detailed. This method has the
advantage of being able to be carried out in a remote place such as the one
where the detectors are deployed. High efficiency results, i.e. 98 % efficiency
for the highest tested overvoltage, combined with a low probability of
accidental counting ($\sim$2 %), show a promising performance for this new
system.
