  A large-area Multi-Pixel Photon Counter (MPPC) sensitive to vacuum ultra
violet (VUV) light has been developed for the liquid xenon (LXe) scintillation
detector of the MEG II experiment. The LXe detector is designed to detect the
52.8\,MeV photon from the lepton flavour violating decay $\mu^+ \to
\mathrm{e}^+ \gamma$ and is based on $900\,\ell$ LXe with a highly granular
scintillation readout by 4092 VUV-MPPCs with an active area of
$139\,\mathrm{mm}^2$ each, totalling $0.57\,\mathrm{m}^2$. The VUV-MPPC shows
an excellent performance in LXe, which includes a high photon detection
efficiency (PDE) up to 21\% for the LXe scintillation light in the VUV range, a
high gain, a low probability of the optical cross-talk and the after-pulsing, a
low dark count rate and a good single photoelectron resolution. The large
active area of the VUV-MPPC is formed by connecting four independent small
VUV-MPPC chips in series to avoid the increase of the sensor capacitance and
thus, to have a short pulse-decay-time, which is crucial for high rate
experiments. Performance tests of 4180 VUV-MPPCs produced for the LXe detector
were also carried out at room temperature prior to the installation to the
detector and all of them with only a few exceptions were found to work
properly. The design and performance of the VUV-MPPC are described in detail as
well as the results from the performance tests at room temperature.
