Three Novel Technical Strategies for Increasing Quantum Efficiency of SiPM at Ultraviolet Wavelength Range
Yuguo Tao
Abstract: Operating with scintillators, SiPM have become very active in the investigation area of nuclear instruments and methods as an alternative to photomultiplier tube (PMT) to detect light with very low intensity. However, the peak value of photo-detection efficiency (PDE) of conventional SiPM is still limited to around 50%. Among the efficiency limiting factors are avalanche triggering probability, geometrical fill factor, and quantum efficiency (QE), which is limited to 80% at the peak. Furthermore, QE is rapidly reduced from the peak value as the wavelength enters ultraviolet range, due to three main factors: (1) photon losses due to the reflection at Si surface with conventional antireflection coatings SiNx layer; (2) surface recombination of the photo-generated primary carriers at the Si surface defect centers passivated with conventional SiO2; (3) Auger recombination of the photo-generated primary carriers within the heavily doped p+ layer prior to transverse to the high field region to trigger an avalanche event. In this project, we will investigate three strategies for increasing quantum efficiency at ultraviolet wavelength range: multi-layer antireflection coatings, Si surface passivation, and selective emitter. The first two specifically will require atomic layer deposition (ALD) strategies while the last one relies on novel semiconductor design and fabrication. Collectively, our objective is to reveal the materials and device physics that currently limit overcoming the fundamental bottlenecks (photon reflection and carrier recombination), and to demonstrate high device performance for ultraviolet sensitive SiPM.