Sensitvity leap for far ultraviolet single photon avalanche diodes

2015年诺贝尔物理学奖是因为发现中微子有质量而获奖。但它们的绝对质量仍然未知。中微子Majorana费米子是一种同时是物质和反物质的理论粒子类型吗？天体粒子物理学领域的目标是在未来几年回答这些关键问题。所需的实验包括大量低温下的液体Xe或Ar和4到100平方米的紫外线敏感光电探测器。*对于仪器工程师来说，这意味着要创造一台具有许多平方米敏感区域的相机，以计算液体Xe或Ar闪烁向各个方向发射的少数紫外光光子。被确定制造这款相机的技术是基于硅制成的单光子雪崩二极管(SPAD)。我领导了一种名为3DdSiPM的独特的全数字光子计数概念的制造，它将使扩大到许多平方米成为可能。所有硅基SPAD探测器的一个限制问题是光电二极管本身在VUV范围内(100-200 nm)的灵敏度。*我的研究计划的目标是将SPAD探测器的灵敏度提高至少三倍。为此，将使用适合大规模生产的特殊外延技术来设计SPAD的导带轮廓。这种方法使ccd在VUV范围内表现得非常好。还将使用原子层沉积技术在SPAD表面制备减反射膜。这项技术可以在极短的真空紫外光波长下构建抗反射多层结构所需的极薄的层。*将基于SPAD的探测器的灵敏度提高三倍将改变许多天体粒子物理实验的游戏规则。它还将通过启用称为飞行时间位置-发射-断层扫描(ToF-PET)的新技术来刺激医学成像领域，使检查更快，辐射剂量更低。**

The 2015 Nobel prize in physics was awarded for the discovery that neutrinos have mass. But their absolute mass is still unknown. Are neutrinos Majorana fermions, a theoretical particle type which is simultaneously matter and anti-matter? The field of astroparticle physics aims to answer these key questions in the coming years. The required experiments involve huge volumes of liquid Xe or Ar at cryogenic temperatures and 4 to 100 m2 of ultraviolet sensitive photodetectors.***For an instrumentation engineer, this translates into creating a camera that has many m2 of sensitive area to count each of the few ultraviolet photons emitted in all direction by the liquid Xe or Ar scintillation. The technology identified to make this camera is based on Single Photon Avalanche Diodes (SPAD) made of silicon. I led the fabrication of a unique concept of fully digital photon counting called 3DdSiPM that will make scaling up to many m2 possible. A limiting issue for all silicon based SPAD detectors is the sensitivity of the photodiodes themselves in the VUV range (100-200 nm).***The objective of my research program is to boost the sensitivity of SPAD detectors by at least a factor of three. To do so, special epitaxial techniques suited for mass production will be used to engineer the conduction band profile of the SPAD. This approach has allowed CCDs to perform very well in the VUV range. Antireflection coating of the surface of the SPAD will also be fabricated using the Atomic Layer Deposition technique. This technique can build the extremely thin layers needed to construct the antireflection multilayer structure for very short VUV wavelengths.***Tripling the sensitivity of SPAD based detectors would be a game changer in many astroparticle physics experiments. It will also stimulate the field of medical imaging by enabling new techniques called Time-of-Flight Position-Emission-Tomography (ToF-PET) to make exams faster and the radiation dose lower. **