Status of HgCdTe Bicolor and Dual-Band Infrared Focal Arrays at LETI

In this paper we show the latest achievements of HgCdTe-based infrared bispectral focal plane arrays (FPAs) at LETI infrared laboratory. We present and compare the two different pixel architectures that are studied now in our laboratory, named “NPN” and “pseudo-planar”. With these two technologies, a wide range of system applications in dual-band detection can be covered. Advantages of both architectures will be pointed out. We also review performances obtained with these different architectures. The first one has been studied for several years in our laboratory, and we review results obtained on FPAs of size 256 × 256 pixels on a 25 μm pitch, in the MWIR/MWIR (3 μm/5 μm) range. Very high noise equivalent temperature difference (NETD) operability is obtained, at 99.8% for the λ_c = 3 μm band and 98.7% for the λ_c = 5 μm band. The second one has been developed more recently, to address other applications that need temporal coherence as well as spatial coherence. We show detailed performances measured on pseudo-planar type FPAs of size 256 × 256 pixels on a 30 μm pitch, in the MWIR/LWIR (5 μm/9 μm) range. The results are also very promising for these prototypes, with NETD as low as 15 mK for an integration time as short as 1 ms, and good operability. The main manufacturing issues are also presented and discussed for both pixel architectures. Challenging process steps are, firstly, molecular beam epitaxy (MBE) HgCdTe heterostructure growth, on large substrates (cadmium zinc telluride) and heterosubstrates (germanium), and, secondly, detector array fabrication on a nonplanar surface. In particular, trenches or hole etching steps, photolithography and hybridization are crucial to improve uniformity, number of defects and performances. Some results of surface, structural and electrical characterizations are shown to illustrate these issues. On the basis of these results, the short-term and long-term objectives and trends for our research and development are presented, in terms of pixel pitch reduction, wavelengths, and dual-band FPA size.     

近红外256×1元InGaAs焦平面探测器无效像元研究

采用分子束外延方法生长的PIN型InP/InGaAs/InP双异质结材料制备了正照射256×1元近红外探测器,并与128×1奇偶两路读出电路互连,制备了近红外256×1元焦平面探测器.针对近红外InGaAs焦平面探测器中的无效像元问题,通过光学显微镜、扫描电镜和电学测试将无效像元进行分类,并分析了无效像元产生的原因.研...     

第三代红外焦平面基础技术的研究进展

叙述了围绕第三代红外焦平面的需求所进行的HgCdTe分子束外延以及台面结芯片技术研究的一些成果。对GaAs、Si基大面积异质外延、p型掺杂以及台面刻蚀等主要难点问题进行了阐述。研究表明,7.6 cm(3 in)材料的组分均匀性良好,晶格失配引发的孪晶缺陷可以通过合适的低温成核方法得到有效抑制。在GaAs和Si衬底上外延的HgCdTe材料的(422)X射线衍射半峰宽的典型值为55″~75″。对ICP技术刻蚀HgCdTe的表面形貌、刻蚀速率、反应微观机理、负载效应和刻蚀延迟效应以及刻蚀损伤进行了研究,得到了高选择比的掩模技术和表面光亮、各向异性较好的刻蚀形貌。采用HgCdTe多层材料试制了长波n?蛳on?蛳p以及p?蛳on?蛳n型掺杂异质结器件以及双色红外短波/中波焦平面探测器,取得了一些初步结果。     

系统中陀螺信号的三种滤波方法

在凝视扫描系统中,大惯量反射镜与快速控制反射镜的速度匹配非常重要。陀螺的输出噪声影响两者的速度匹配,于是陀螺输出信号的滤波就成了首要的问题。通过对三种滤波方法的研究,结果表明:小波收缩去噪具有更好的信噪分离效果。