Preliminary results for the design,fabrication,and performance of a backside-illuminated avalanche drift detector

The detection of low-level light is a key technology in various experimental scientific studies.As a photon detector,the silicon photomultiplier(SiPM) has gradually become an alternative to the photomultiplier tube(PMT) in many applications in high-energy physics,astroparticle physics,and medical imaging because of its high photon detection efficiency(PDE),good resolution for single-photon detection,insensitivity to magnetic field,low operating voltage,compactness,and low cost.However,primarily because of the geometric fill factor,the PDE of most SiPMs is not very high; in particular,for those SiPMs with a high density of micro cells,the effective area is small,and the bandwidth of the light response is narrow.As a building block of the SiPM,the concept of the backside-illuminated avalanche drift detector(ADD) was first proposed by the Max Planck Institute of Germany eight years ago; the ADD is promising to have high PDE over the full energy range of optical photons,even ultraviolet light and X-ray light,and because the avalanche multiplication region is very small,the ADD is beneficial for the fabrication of large-area SiPMs.However,because of difficulties in design and fabrication,no significant progress had been made,and the concept had not yet been verified.In this paper,preliminary results in the design,fabrication,and performance of a backside-illuminated ADD are reported; the difficulties in and limitations to the backside-illuminated ADD are analyzed.