混合式光电探测器

Review of Hybrid Photodetector

混合式探测器(Hybrid Photodetector,HPD)作为一种新型的光电探测器件,是真空与半导体类结合型探测器件。HPD包括沉积在输入光窗表面的光电探测阴极、固态半导体阳极芯片和保持系统真空度的固态阳极。工作时,光信号通过沉积在输入光窗表面的光电阴极转化为光电子,经过高能电场加速后获得高能量轰击阳极半导体芯片表面,产生大量的电子空穴对,电子空穴对在半导体内部进行迁移,并通过自身的雪崩效应实现倍增,最终以电流信号输出。该探测器摒弃了传统的光电倍增管的微通道板(Micro Channel Plate,MCP)等倍增器件,克服了倍增单元信号易饱和的缺陷,增大了探测器的动态范围。HPD探测器综合了光电倍增管的高灵敏度和半导体芯片优异的空间和能量分辨率,具有探测面积大、探测灵敏度高、倍增效应强、动态范围宽等优点。在高能物理、医学成像和天体物理中有着重要的应用。此外,该探测器具有多种结构,分为近贴聚焦结构、交叉聚焦结构和漏斗聚焦结构,能够满足不同使用范围的探测需求;随着半导体阳极技术的发展,HPD阳极从单一芯片逐渐过渡到阵列式阳极结构,满足了大面积探测的需求。同时数字式读出和倍增信号技术的封装技术的发展,提高了HPD探测器的信号倍增和读出速度,改善了器件的集成化程度,有利于探测信号读出速率和信噪比的提升。近年来,其单光子计数和高动态响应等能力逐步被重视,将会在未来的光电探测领域发挥更为重要的作用。

Hybrid Photodetector （HPD） is a new generation detector, which combines the vacuum and semiconductor technologies. HPD consists of a vacuum envelop, a photocathode de- posited on the input window and solid silicon sensors. When working , a photocathode which is deposited on the inner side of the window converts light quanta from the photocathode and is accelerated by a high energy potential difference AV of the order of dozens of kV directly onto the silicon sensor , which is usually kept at ground potential. The electric field can be shaped by means of electrodes in order to obtain certain electron-optical properties, e.g. a linear demagnifi-cation between the photocathode and the silicon sensor. The absorbed kinetic energy of the photoelectron gives rise to the creation of electron-hole pairs, which results in a detectable current in the depleted silicon sensor. The New developed HPD abandons the multiplication part of the traditional in the photomultiplication tube, e.g. micro channel plate （MCP） and overcomes the defects such as signal saturation and enlarge the dynamic range of the photodetector. The HPD is of the high detector sensitivities of the vacuum tubes and the excellent spatial and energy resolution of the silicon sensors, showing advantages of large detect area, high detect sensitivity, large mul- tiplication and broad dynamic range. These advantages make the HPD a wide application candidate in high energy physics, medical imaging and astrophysics. Furthermore, HPD has a various structures such as proximity focusing, cross focusing and funnel focusing, which can cover different useable range in different conditions. With the development of the semiconductor anode, the HPD develops from single anode to multiple anode arrays, making the HPD detector qualified for the need of the large detect areas. At the same time the integrated level of the HPD detector promotes with the improvements in the digital read-out techniques and speed, which will be helpful to the readout speed and signal to noise ratio. In recent years, the HPD attracts much more attentions due to its excellent photon counting and wide dynamic range, which will find more application in the photodetector in the future.