In order to meet the requirements of the High Luminosity LHC (HL-LHC), it
will be necessary to replace the current tracker of the ATLAS experiment.
Therefore, a new all-silicon tracking detector is being developed, the
so-called Inner Tracker (ITk). The use of quad chip modules is intended in its
pixel region. These modules consist of a silicon sensor that forms a unit along
with four read-out chips. The current ATLAS pixel detector consists of planar
n-in-n silicon pixel sensors. Similar sensors and four FE-I4 read-out chips
were assembled to first prototypes of planar n-in-n quad modules. The main
focus of the investigation of these modules was the region between the read-out
chips, especially the central area between all four read-out chips. There are
special pixel cells placed on the sensor which cover the gap between the
read-out chips. This contribution focuses on the characterization of a
non-irradiated device, including important sensor characteristics, charge
collection determined with radioactive sources as well as hit efficiency
measurements, performed in the laboratory and at testbeams. In addition, first
laboratory results of an irradiated device are presented
