Discussion about photodiode architectures for space applications
Discussion about photodiode architectures for space applications
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关于空间应用光电二极管架构的讨论
DOI：
10.1117/12.2304266
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
O. Boulade
中科院分区：
文献类型：
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作者：
O. Gravrand;G. Destefanis;C. Cervera;J. Zanatta;N. Baier;A. Ferron;O. Boulade
空间应用对红外探测器的探测要求非常高：从可见光近红外(2-3um截止)到长波IR(10-12.5um截止)，甚至有时VLWIR(15um截止)，所有波长都可能是令人感兴趣的。此外，通常会考虑各种情况。有些是成像应用，其中焦平面阵列(FPA)被用作光学元件来感测图像。然而，FPA也可以用于光谱测量应用中，其中光根据其波长在不同的像素上被触发。在某些情况下，指向恒星是FPA的另一种用途，视网膜被用来感知卫星的位置。在所有这些配置中，我们可能会区分几类应用程序：·低通量应用程序，即FPA凝视太空，仅用几个光子进行检测。·FPA通常盯着地球的高通量应用。在这种情况下，地球及其大气的黑体发射通常确保了大量光子来执行探测。这两个不同的类别对探测器具有很高的尺寸，因为它通常决定暗电流的水平和量子效率(QE)要求。事实上，高检测性能通常需要大量的积分光子，因此对于低通量应用需要高QE，以便尽可能地限制积分时间。此外，暗电流要求还与预期的入射通量直接相关，以便尽可能地限制由于暗电荷与光电荷引起的信噪比下降。请注意，在大多数情况下，该暗电流高度依赖于控制探测器消耗的工作温度。缓解暗电流的一个经典方法是将探测器冷却到非常低的温度。这篇文章不会讨论波前传感的必要性，因为由于积分窗口非常窄，检测到的光子数很少。严格地说，这种配置是低通量应用，但对速度的需求使其有别于其他低通量应用，因为它通常需要不同的ROIC架构和针对高响应速度优化的光电二极管。
Detection for space application is very demanding on the IR detector: all wavelengths, from visible-NIR (2- 3um cutoff) to LWIR (10-12.5um cutoff), even sometimes VLWIR (15um cutoff) may be of interest. Moreover, various scenarii are usually considered. Some are imaging applications where the focal plane array (FPA) is used as an optical element to sense an image. However, the FPA may also be used in spectrometric applications where light is triggered on the different pixels depending on its wavelength. In some cases, star pointing is another use of FPAs where the retina is used to sense the position of the satellite. In all those configurations, we might distinguish several categories of applications: • low flux applications where the FPA is staring at space and the detection occurs with only a few number of photons. • high flux applications where the FPA is usually staring at the earth. In this case, the black body emission of the earth and its atmosphere ensures usually a large number of photons to perform the detection. Those two different categories are highly dimensioning for the detector as it usually determines the level of dark current and quantum efficiency (QE) requirements. Indeed, high detection performance usually requires a large number of integrated photons such that high QE is needed for low flux applications, in order to limit the integration time as much as possible. Moreover, dark current requirement is also directly linked to the expected incoming flux, in order to limit as much as possible the SNR degradation due to dark charges vs photocharges. Note that in most cases, this dark current is highly depending on operating temperature which dominates detector consumption. A classical way to mitigate dark current is to cool down the detector to very low temperatures. This paper won't discuss the need for wavefront sensing where the number of detected photons is low because of a very narrow integration window. Rigorously, this kind of configuration is a low flux application but the need for speed distinguishes it from other low flux applications as it usually requires a different ROIC architecture and a photodiode optimized for high response speed.