New Infrared Detectors for Astrophysics

以HgCdTe作为光敏层的红外阵列，例如已经为詹姆斯·韦伯太空望远镜开发了高达2048 x2048像素的尺寸，是在~1-5微米区域内成像和光谱学的接近理想的探测器。 然而，目前的构造需要在CdZnTe衬底上制造，这是昂贵的且可用性有限。 制造更大（高达14，000 × 14，000像素）和更便宜的红外探测器的关键在于使用硅片衬底，因为大硅片在大批量半导体工业中很常见，并且它们的热膨胀系数与硅读出电路的热膨胀系数很好地匹配。 虽然硅衬底的使用一直是红外探测器开发领域的主要目标，但在过去15年中的主要限制是硅和常用的红外光敏材料之间的大晶格间距失配。这种不匹配会导致缺陷，从而导致更高的暗电流，或者导致量子效率和图像持久性降低的价空穴。罗切斯特理工学院的菲格计划使用非常有前途的分子束外延（MBE）技术在硅上存款碲镉汞光敏层。 通过在MBE工艺期间保持真空，已显示出缺陷密度降低，并且所得原型器件已实现预期性能。 非常大的，负担得起的红外线阵列将是必要的，以最佳利用拟议的~ 30米级地面望远镜和他们的可用性有明显的影响，天文学以外的领域，包括医学成像和遥感。用于硅上大型红外阵列开发的资金由NSF天文科学部通过其先进技术和仪器计划提供。

Infrared arrays with HgCdTe as the light-sensitive layer, such as have been developed up to sizes 2048x2048 pixels for the James Webb Space Telescope, are near-ideal detectors for imaging and spectroscopy in the region ~1-5 microns. However current construction requires fabrication on CdZnTe substrates, which are expensive and limited in availability. The key to making larger (up to 14,000x14,000 pixels) and less expensive infrared detectors lies in using silicon wafer substrates, since large silicon wafers are common in the high volume semiconductor industry and their coefficient of thermal expansion is well-matched to that of the silicon readout circuits. While the use of silicon substrates has been a major goal in the field of developing infrared detectors, the main limitation over the past 15 years has been the large lattice spacing mismatch between silicon and commonly-used infrared light-sensitive materials. The mismatch causes defects that can result in higher dark current, or valence holes that lead to reduced quantum efficiency and image persistence.Enlisting the expertise and fabrication capabilities of Raytheon Vision Systems, detector expert Dr. D. Figer of the Rochester Institute of Technology plans to deposit the HgCdTe light-sensitive layer on silicon using the very promising technique of Molecular Beam Epitaxy (MBE). By maintaining vacuum during MBE processing, defect density has been shown to be reduced and the resulting prototype devices have achieved the anticipated performance. Very large, affordable infrared arrays will be essential for making optimum use of the proposed ~30m class ground-based telescopes and their availability has clear implications for fields beyond astronomy, including medical imaging and remote sensing. Funding for the development of large infrared arrays on silicon is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.