Sub-electron read noise and millisecond full-frame readout with the near infrared eAPD array SAPHIRA
Sub-electron read noise and millisecond full-frame readout with the near infrared eAPD array SAPHIRA
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使用近红外 eAPD 阵列 SAPHIRA 实现亚电子读取噪声和毫秒全帧读出
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发表时间：
2016
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通讯作者：
H. Weller
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作者：
G. Finger;I. Baker;D. Álvarez;C. Dupuy;D. Ives;M. Meyer;L. Mehrgan;J. Stegmeier;H. Weller
2007年，ESO在SELEX（现在的LEONARDO）启动了一个项目，开发无噪声的近红外HgCdTe电子雪崩光电二极管阵列（eAPD）[1][2][3]。这种eAPD技术是克服用于波前传感和条纹跟踪的近红外传感器的CMOS噪声障碍的唯一方法。经过几个固态工程技术的发展周期，可以很容易地应用于金属有机气相外延（MOVPE）生长技术的选择，eAPD阵列已经成熟，并产生了SAPHIRA阵列。它们的格式为320x256像素，间距为24 μm。它们现在以毫秒帧读出速率提供无与伦比的亚电子读取噪声组合。第一代sapira阵列仅在H和k波段敏感。随着宽带隙缓冲层的去除，阵列现在在λ=0.8 μm到2.5 μm范围内敏感，在整个波长范围内具有高量子效率。在生长过程中应用的高温退火产生的材料具有极好的美容质量，APD增益超过600。SAPHIRA ROIC的设计也进行了修订，新的ME1000 ROIC具有优化的模拟链和更灵活的读出模式。垂直移位寄存器的时钟现在处于外部控制之下。这样做的好处是，在滚动快门模式下，相关的双采样和不相关的读出现在在最大帧速率下具有100%的占空比。此外，为了减少读出噪声，可以在行复位前后多次读取行。由于APD增益足够高，一个光子产生的电子比重置后的电荷不确定度kTC的平方根要多，因此每次曝光一个光子的信号可以很容易地检测到，而不需要双重相关采样。利用重力条纹跟踪器和安装在VLTI 4个8米望远镜CIAO自适应光学系统中的4个sapira波前传感器获得的初步结果证明了sapira eAPD技术无与伦比的性能。一个未来的项目正在组装，以开发具有1Kx1K更大格式的eAPD阵列，能够实现1.2 KHz的帧速率。低暗电流eAPD技术在大画幅科学焦平面上也有很好的应用前景。
In 2007 ESO started a program at SELEX (now LEONARDO) to develop noiseless near infrared HgCdTe electron avalanche photodiode arrays (eAPD)[1][2][3]. This eAPD technology is only way to overcome the limiting CMOS noise barrier of near infrared sensors used for wavefront sensing and fringe tracking. After several development cycles of solid state engineering techniques which can be easily applied to the chosen growth technology of metal organic vapour phase epitaxy (MOVPE), the eAPD arrays have matured and resulted in the SAPHIRA arrays. They have a format of 320x256 pixels with a pitch of 24 μm. They now offer an unmatched combination of sub-electron read noise at millisecond frame readout rates. The first generation of SAPHIRA arrays were only sensitive in H and K-band. With the removal of a wide bandgap buffer layer the arrays are now sensitive from λ=0.8 μm to 2.5 μm with high quantum efficiency over the entire wavelength range. The high temperature anneal applied during the growth process produces material with superb cosmetic quality at an APD gain of over 600. The design of the SAPHIRA ROIC has also been revised and the new ME1000 ROIC has an optimized analogue chain and more flexible readout modes. The clock for the vertical shift register is now under external control. The advantage of this is that correlated-double-sampling and uncorrelated readout in the rolling shutter mode now have a duty cycle of 100% at the maximum frame rate. Furthermore, to reduce the readout noise rows can be read several times before and after row reset. Since the APD gain is sufficiently high that one photon produces many more electrons than the square root of kTC which is the charge uncertainty after reset, signals of one photon per exposure can be easily detected without the need for double correlated sampling. First results obtained with the fringe tracker in GRAVITY and the four SAPHIRA wavefront sensors installed in the CIAO adaptive optics systems of the four 8 meter telescopes of the VLTI have proven the unrivaled performance of the SAPHIRA eAPD technology. A future program is being assembled to develop eAPD arrays having a larger format of 1Kx1K capable of frame rates of 1.2 KHz. There are also good prospects to offer low dark current eAPD technology for large format science focal planes as well.