SWIR HgCdTe avalanche photiode focal plane array performances evaluation
SWIR HgCdTe avalanche photiode focal plane array performances evaluation
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SWIR HgCdTe雪崩光电焦平面阵列性能评估
DOI：
10.1117/12.2304265
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
P. Feautrier
中科院分区：
文献类型：
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作者：
E. de Borniol;J. Rothman;F. Salveti;P. Feautrier
自适应光学（AO）系统或条纹跟踪仪等现代天文仪器的主要挑战之一是处理非常低的光子通量探测场景。大气辐射的典型时间尺度在几十毫秒的范围内，用于AO系统的红外波前传感器需要高于1 KHz的帧速率，导致积分时间低于1 ms。与低辐照度相关的这种积分时间导致每帧每像素的积分光子数很少。为了保留来自这种弱信号的信息，焦平面阵列（FPA）必须呈现低读出噪声、高量子效率和低暗电流。到目前为止，高速近红外传感器的输出噪声受到硅读出电路噪声的限制。因此，使用在中等反向偏压下具有高增益和低过量噪声的HgCdTe雪崩光电二极管似乎是降低读取噪声对图像信噪比的影响的合乎逻辑的方式。这些具有毫秒级积分时间的低辐照度无源成像应用需要低光电二极管暗电流和低背景电流。这些要求导致光电二极管截止波长的选择。3 μm附近的短波红外（SWIR）是在给定APD偏压下可以获得的增益与背景和暗电流之间的良好折衷。CEA LETI HgCdTe APD技术和增益曲线特性的精细分析在[1]中给出，此处不再详述。APD的响应时间也是高帧率FPA的关键因素。该参数已在[2]中进行了评估，结果显示截止频率在GHz范围内。本文介绍了由CEA LETI和SOFRADIR公司研制的用于天体物理应用的短波红外APD焦平面阵列的性能。这项开发是在RAPID的框架内进行的，RAPID是一个由法国FUI（Fond Unique Interministériel）资助的4年研发项目。该项目涉及先进红外焦平面阵列制造领域（SOFRADIR和CEA LETI）和天文/国防研究所（IPAG，LAM，ONERA）的工业和学术合作伙伴。该计划的目标是开发一种快速、低噪声的短波红外相机，用于天文快速应用，例如自适应光学波前传感和天文干涉仪的条纹跟踪[3]。第一批焦平面阵列是基于液相外延（LPE）生长的截止波长为3 μm的光电二极管阵列。为了在给定的光电二极管反向偏置电压下获得更高的雪崩增益，我们用镉组分制备了第二批，其截止波长（λc）为3.3 μm。本文在下一节中描述了读出电路。第三部分的目的是找到必须测量的关键参数，以评估APD焦平面的信噪比（SNR）。在“快速表征焦平面阵列”一节中介绍了基于3.3μm截止波长APD的焦平面阵列的主要电光特性。详细分析了3 μ mFPA在APD高、低偏压下暗电流随温度的变化。
One of the main challenges of modern astronomical instruments like adaptive optics (AO) systems or fringe trackers is to deal with the very low photons flux detection scenarios. The typical timescale of atmospheric turbulences being in the range of some tens of milliseconds, infrared wavefront sensors for AO systems needs frame rates higher than 1 KHz leading to integration times lower than 1 ms. This integration time associated with a low irradiance results in a few number of integrated photons per frame per pixel. To preserve the information coming from this weak signal, the focal plane array (FPA) has to present a low read out noise, a high quantum efficiency and a low dark current. Up to now, the output noise of high speed near infrared sensors is limited by the silicon read out circuit noise. The use of HgCdTe avalanche photodiodes with high gain at moderate reverse bias and low excess noise seems then a logical way to reduce the impact of the read noise on images signal to noise ratio. These low irradiance passive imaging applications with integration times in the millisecond range needs low photodiode dark current and low background current. These requirements lead to the choice of the photodiode cut off wavelength. The short wave infrared (SWIR) around 3 μm is a good compromise between the gain that can be obtain for a given APD bias and the background and dark current. The CEA LETI HgCdTe APD technology, and a fine analysis of the gain curve characteristic are presented in [1] and won’t be detailed here. The response time of the APD is also a key factor for a high frame rate FPA. This parameter has been evaluated in [2] and the results shows cut off frequencies in the GHz range. In this communication we report the performances of a SWIR APD FPA designed and fabricated by CEA LETI and SOFRADIR for astrophysical applications. This development was made in the frame of RAPID, a 4 years R&D project funded by the French FUI (Fond Unique Interministériel). This project involves industrial and academic partners from the field of advanced infrared focal plane arrays fabrication (SOFRADIR and CEA LETI) and of astronomical/defense institutes (IPAG, LAM, ONERA). The goal of this program is to develop a fast and low noise SWIR camera for astronomical fast applications like adaptive optics wavefront sensing and fringe tracking for astronomical interferometers [3]. The first batch of FPA’s was based on liquid-phase epitaxy (LPE) grown photodiode arrays with 3 μm cut off wavelength. In order to get higher avalanche gain for a given photodiode reverse bias voltage, we have made a second batch with a cadmium composition leading to 3.3 μm cut off wavelength (λc). This paper described the read out circuit in the next section. The aim section III is to find the critical parameter that has to be measured to evaluate the signal to noise ratio (SNR) of an APD FPA. The main electro optical characteristics of an FPA based on 3.3μm cut off wavelength APDs are reported in “Rapid FPAs characterisation” section. The dark current evolution with temperature of a 3 μm FPA high and low APD bias is also detailed in this section.