[论文解读] Persistence Characterisation of teledyne H2RG detectors

Simon Tulloch|arXiv (Cornell University)|Jul 13, 2018

Photonic and Optical Devices参考文献 1被引用 9

一句话总结

本研究通过在低背景低温恒温器中使用LED照射，对Teledyne H2RG红外探测器中的电荷持续现象进行了表征，测量了不同曝光水平下的陷阱捕获与释放动力学。研究识别出两种不同的陷阱群体——一种为快速捕获、缓慢释放电荷（持续数小时），另一种为捕获与释放速率平衡的陷阱——并提供了时间常数谱，使数据处理流程中的持续现象校正得以改进，且较低温度和降低偏置电压可显著减少持续现象。

ABSTRACT

Image persistence is a major problem in infrared detectors, potentially seriously limiting data quality in many observational regimes. The problem manifests itself as remnant images that can persist for several days after a deep exposure. In this study, the persistence behavior of three 5.3um cutoff H2RGs has been characterised using a low-background cryostat with LED light sources. Persistence charge de-trapping was measured over several hours following a wide range of exposure levels and exposure times. This data was then analysed to yield charge trapping and de-trapping spectra which present graphically the trap density as a function of their time constants. These spectra show the detector behavior in a very direct way and offer a natural metric for comparing different devices. It is hoped that the trap time constant spectra for each detector can be used in an analysis pipeline to remove persistence artifacts based on the recent exposure history of the detector. The study confirmed that the charge traps responsible for persistence must be present in the depletion region of the pixel, however, two trap populations were revealed. One of these captures charge within milliseconds and then releases it over many hours. The second population is less problematic with fairly similar trapping and de-trapping time constants. Large differences in persistence magnitude and trap spectra have been found even between devices with near-consecutive serial numbers. Lower temperatures resulted in lower persistence both in terms of total trapped charge and the time taken for that charge to decay. Limiting the full-well by reducing pixel bias voltage also had a beneficial effect. Previously proposed mitigation techniques including "global reset de-trapping" and "night light" illumination were tried but found to be ineffective.

研究动机与目标

• 理解Teledyne H2RG红外探测器中图像持续现象背后的物理机制。
• 通过受控低温测试，量化不同曝光水平和持续时间下的持续现象行为。
• 开发陷阱时间常数谱作为设备特异性指标，用于持续现象建模与校正。
• 评估现有缓解技术（如全局复位去陷阱和夜间光照）的有效性。
• 评估温度和像素偏置电压对持续现象幅度和衰减时间的影响。

提出的方法

• 使用校准的LED光源对三台5.3 µm截止波长的H2RG探测器进行低背景低温恒温器实验。
• 施加广泛的曝光水平和持续时间，以模拟深空曝光，并测量电荷持续衰减过程中的小时级变化。
• 测量电荷去陷阱速率，通过光谱分析推导陷阱能级和时间常数分布。
• 生成作为时间常数函数的陷阱密度谱，以可视化和比较不同设备间的陷阱群体。
• 评估包括全局复位去陷阱和连续夜间光照在内的缓解策略。
• 改变探测器温度和像素偏置电压，以评估其对总捕获电荷量和衰减时间的影响。

实验结果

研究问题

• RQ1 H2RG探测器中导致持续现象的主要陷阱群体是什么？它们的时间常数有何差异？
• RQ2 曝光水平和持续时间如何影响持续电荷的幅度和衰减特性？
• RQ3 温度和像素偏置电压在多大程度上可减少H2RG探测器的持续现象？
• RQ4 为何具有相邻序列号的H2RG探测器在持续现象行为上表现出显著差异？
• RQ5 既有的缓解技术（如全局复位去陷阱和夜间光照）在减少持续现象方面是否有效？

主要发现

• 识别出两种不同的陷阱群体：一种为毫秒级捕获、数小时级去陷阱（极具问题），另一种为捕获与去陷阱速率平衡（危害较小）。
• 即使在序列号接近的H2RG之间，持续现象幅度和陷阱谱也存在显著差异，表明器件间存在明显差异。
• 较低的工作温度可同时减少总捕获电荷量和电荷衰减所需时间，从而改善持续现象性能。
• 通过降低像素偏置电压减少满阱容量，同样可减少持续现象，表明这是一种可在设计阶段实施的缓解策略。
• 在测试条件下，全局复位去陷阱和夜间光照均未能有效缓解持续现象。
• 陷阱时间常数谱为数据处理流程中的持续现象建模与校正提供了直接且设备特异性的指标。