Organisation Européenne Pour la Recherche Nucléaire, Experimental Physics Department, Esplanade des Particules 1, 1211 Meyrin, Switzerland.
Escuela de Ciencias, Ingeniería y Diseño, Universidad Europea de Valencia, Passeig de l'Albereda, 7, 46010 Valencia, Spain.
Sensors (Basel). 2021 Dec 24;22(1):122. doi: 10.3390/s22010122.
Silicon photomultipliers (SiPMs) are arrays of single-photon avalanche diodes (SPADs) connected in parallel. Analog silicon photomultipliers are built in custom technologies optimized for detection efficiency. Digital silicon photomultipliers are built in CMOS technology. Although CMOS SPADs are less sensitive, they can incorporate additional functionality at the sensor plane, which is required in some applications for an accurate detection in terms of energy, timestamp, and spatial location. This additional circuitry comprises active quenching and recharge circuits, pulse combining and counting logic, and a time-to-digital converter. This, together with the disconnection of defective SPADs, results in a reduction of the light-sensitive area. In addition, the pile-up of pulses, in space and in time, translates into additional efficiency losses that are inherent to digital SiPMs. The design of digital SiPMs must include some sort of optimization of the pixel architecture in order to maximize sensitivity. In this paper, we identify the most relevant variables that determine the influence of SPAD yield, fill factor loss, and spatial and temporal pile-up in the photon detection efficiency. An optimum of 8% is found for different pixel sizes. The potential benefits of molecular imaging of these optimized and small-sized pixels with independent timestamping capabilities are also analyzed.
硅光电倍增管 (SiPM) 是由多个单光子雪崩二极管 (SPAD) 并联组成的阵列。模拟硅光电倍增管是基于优化探测效率的定制技术构建的。数字硅光电倍增管则是基于 CMOS 技术构建的。尽管 CMOS SPAD 的灵敏度较低，但它们可以在传感器平面上集成额外的功能，这在某些应用中对于能量、时间戳和空间位置的精确检测是必需的。这些额外的电路包括有源猝灭和充电电路、脉冲组合和计数逻辑以及时间数字转换器。这与有缺陷的 SPAD 的断开一起导致光敏感区域的减少。此外，脉冲在空间和时间上的堆积会导致数字 SiPM 固有的额外效率损失。数字 SiPM 的设计必须包括某种像素架构的优化，以最大程度地提高灵敏度。在本文中，我们确定了决定 SPAD 产量、填充因子损失以及光子探测效率的空间和时间堆积影响的最相关变量。针对不同的像素尺寸，我们找到了 8%的最佳值。我们还分析了这些优化后的小型像素具有独立时间戳功能的分子成像的潜在优势。
