  Photomultipliers (PMTs) are currently adopted for the photodetector plane of
Imaging Atmospheric Cherenkov Telescopes (IACTs). Even though PMT quantum
efficiency has improved impressively in the recent years, one of the main
limitation for their application in the gamma-astronomy field - the
impossibility to operate with moon light - still remains. As a matter of fact,
the light excess would lead to significant and faster camera ageing. Solid
state detectors, in particular Geiger-mode avalanche photo-diodes (G-APDs)
represent a valuable alternative solution to overcome this limitation as
demonstrated in the field by the FACT experiment (The First G- APD Cherenkov
Telescope). They can be regarded as a more promising long term approach, which
can be easily adopted for the new generation of cameras and for the Cherenkov
Telescope Array (CTA). We describe here the Photo-Detector Plane (PDP) of the
camera for the 4 m Davies Cotton CTA Small Size Telescopes, for which large
area G-APD coupled to non-imaging light concentrators are planned. The PDP
includes 1296 photosensors, the biasing and pre-amplification stages, the
control electronics as well as the mechanical support and the water- tight
enclosure. We developed with Hamamatsu a new large area hexagonal shaped G-APD
with an area of 93.6 mm^2. This G-APD is divided into 4 channels which will be
summed after the pre-amplification stage to maintain an acceptable time
characteristic of the signal. The characterization of this device for 50 um and
100 um micro-cell sizes will be discussed and compared to other non-custom
photodetectors.
