HgCdTe heterostructures on Si (310) substrates for midinfrared focal plane arrays (original) (raw)
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HgCdTe heterostructures on Si(310) substrates for infrared photodetectors
Optoelectronics, Instrumentation and Data Processing, 2009
Molecular beam epitaxial growth of HgCdTe solid solutions on silicon substrates of 76.2 mm diameter was studied. Conditions for producing HgCdTe/Si(310) heterostructures for the spectral range of 3-5 μm which are suitable for fabricating high-quality devices were determined. A 4 × 288 photodetector was fabricated by hybrid assembly of an array photosensitive element with a multiplexer. Results on the sensitivity and stability of this photodetector to thermal cycling are given.
High-Performance LWIR MBE-Grown HgCdTe/Si Focal Plane Arrays
Journal of Electronic Materials, 2007
We have been actively pursuing the development of long-wavelength infrared (LWIR) HgCdTe grown by molecular beam epitaxy (MBE) on large-area silicon substrates. The current effort is focused on extending HgCdTe/Si technology to longer wavelengths and lower temperatures. The use of Si versus bulk CdZnTe substrates is being pursued due to the inherent advantages of Si, which include available wafer sizes (as large as 300 mm), lower cost (both for the substrates and number of die per wafer), compatibility with semiconductor processing equipment, and the match of the coefficient of thermal expansion with silicon read-out integrated circuit (ROIC). Raytheon has already demonstrated low-defect, high-quality MBE-grown HgCdTe/Si as large as 150 mm in diameter. The focal plane arrays (FPAs) presented in this paper were grown on 100 mm diameter (211)Si substrates in a Riber Epineat system. The basic device structure is an MBE-grown p-on-n heterojunction device. Growth begins with a CdTe/ZnTe buffer layer followed by the HgCdTe active device layers; the entire growth process is performed in situ to maintain clean interfaces between the various layers. In this experiment the cutoff wavelengths were varied from 10.0 lm to 10.7 lm at 78 K. Detectors with >50% quantum efficiency and R 0 A~1000 Ohms cm 2 were obtained, with 256 · 256, 30 lm focal plane arrays from these detectors demonstrating response operabilities >99%.
IEEE Transactions on Electron Devices, 2000
At the U.S. Army Research Laboratory, a new ternary semiconductor system CdSe x Te 1−x /Si(211) is being investigated as an alternative substrate to bulk-grown CdZnTe substrates for HgCdTe growth by molecular beam epitaxy. Long-wavelength (LW) photovoltaic devices fabricated on this compliant substrate material show diffusion limited performance at 78 K, indicating a high-quality material. The measured R o A at 78 K on λ co = 10 μm material is on the order of 340 Ω · cm 2 . In addition to single devices, we have fabricated 256 × 256 2-D arrays with a 40-μm pixel pitch on LW-HgCdTe grown on CdSe x Te 1−x /Si(211) compliant substrates. The data show an excellent quantum efficiency operability of 99% at 78 K under a tactical background flux of 6.7 × 10 15 ph/cm 2 s. The most probable dark current at peak distribution is 5.5 × 10 9 e-/s and is very consistent with the measured R o A values from single devices. This work demonstrates that CdSe x Te 1−x /Si(211) substrates provide a potential roadmap for more affordable robust third-generation focal plane arrays. Index Terms-CdSeTe, CdTe, compliant Si substrates, focal plane arrays (FPAs), HgCdTe, infrared (IR) detectors, longwavelength IR, molecular beam epitaxy (MBE).
Advances in HgCdTe-based infrared detector materials: the role of molecular-beam epitaxy
SPIE International Symposium on Optical Science and Technology, 2001
Since its initial synthesis and investigation more than 40 years ago, the HgCdTe alloy semiconductor system has evolved into one of the primary infrared detector materials for high-performance infrared focal-plane arrays (FPA) designed to operate in the 3-5 µm and 8-12 µm spectral ranges of importance for thermal imaging systems. Over the course of the past decade, significant advances have been made in the development of thin-film epitaxial growth techniques, such as molecular-beam epitaxy (MBE), which have enabled the synthesis of IR detector device structures with complex doping and composition profiles. The central role played by in situ sensors for monitoring and control of the MBE growth process are reviewed. The development of MBE HgCdTe growth technology is discussed in three particular device applications: avalanche photodiodes for 1.55 µm photodetection, megapixel FPAs on Si substrates, and multispectral IR detectors.
HgCdTe/CdTe/Si infrared photodetectors grown by MBE for near-room temperature operation
Journal of Electronic Materials, 2001
Conventional HgCdTe infrared detectors need significant cooling in order to reduce noise and leakage currents resulting from thermal generation and recombination processes. Although the need for cooling has long been thought to be fundamental and inevitable, it has been recently suggested that Auger recombination and generation rates can be reduced by using the phenomena of exclusion and extraction to produce nonequilibrium carrier distributions. The devices with Auger suppressed operation requires precise control over the composition, and donor and acceptor doping. The successful development of the molecular beam epitaxy (MBE) growth technique for multi-layer HgCdTe makes it possible to grow these device structures. Theoretical calculations suggest that the ppn+ layer sequence is preferable for near-room temperature operation due to longer minority carrier lifetime in lightly doped p-HgCdTe absorber layers. However, because the low doping required for absorption and nonequilibrium operation is easier to achieve in n-type materials, and because Shockley-Read centers should be minimized in order to obtain the benefits of Auger suppression, we have focused on p + nn structures. Planar photodiodes were formed on CdTe/ Si (211) composite substrates by As implantation followed by a three step annealing sequence. Three inch diameter Si substrates were employed since they are of high quality, low cost, and available in large areas. Due to this development, large area focal plane arrays (FPAs) operated at room temperature are possible in the near future. The structures were characterized by FTIR, x-ray diffraction, temperature dependent Hall measurements, minority carrier lifetimes by photoconductive decay, and in-situ ellipsometry. To study the relative influence of bulk and surface effects, devices with active areas from 1.6 ¥ 10 -5 cm 2 to 10 -3 cm 2 were fabricated. The smaller area devices show better performance in terms of reverse bias characteristics indicating that the bulk quality could be further improved. At 80 K, the zero bias leakage current for a 40 mm ¥ 40 mm diode with 3.2 mm cutoff wavelength is 1 pA, the R 0 A product is 1.1 ¥ 10 4 W-cm 2 and the breakdown voltage is in excess of 500 mV. The device shows a responsivity of 1.3 ¥ 10 7 V/W and a 80 K detectivity of 1.9 ¥ 10 11 cm-Hz 1/2 /W. At 200 K, the zero bias leakage current is 5 nA and the R 0 A product 2.03 W-cm 2 , while the breakdown voltage decreases to 40 mV.
Molecular beam epitaxy grown long wavelength infrared HgCdTe on compliant Si substrates
SPIE Proceedings, 2006
The use of silicon as a substrate alternative to bulk CdZnTe for epitaxial growth of HgCdTe for infrared (IR) detector applications is attractive because of potential cost savings as a result of the large available sizes and the relatively low cost of silicon substrates. However, the potential benefits of silicon as a substrate have been difficult to realize because of the technical challenges of growing low defect density HgCdTe on silicon where the lattice mismatch is ϳ19%. This is especially true for LWIR HgCdTe detectors where the performance can be limited by the high (ϳ5 ϫ 10 6 cm Ϫ2) dislocation density typically found in HgCdTe grown on silicon. We have fabricated a series of long wavelength infrared (LWIR) HgCdTe diodes and several LWIR focal plane arrays (FPAs) with HgCdTe grown on silicon substrates using MBE grown CdTe and CdSeTe buffer layers. The detector arrays were fabricated using Rockwell Scientific's planar diode architecture. The diode and FPA and results at 78 K will be discussed in terms of the high dislocation density (ϳ5 ϫ 10 6 cm 2) typically measured when HgCdTe is grown on silicon substrates.
Journal of electronic …, 2001
We have developed the capability to grow HgCdTe mid-wave infrared radiation double-layer heterojunctions (MWIR DLHJs) on 4≤ Si wafers by molecular beam epitaxy (MBE), and fabricate devices from these wafers that are comparable to those produced by mature technologies. Test data show that the detectors, which range in cutoff wavelength over 4-7 mm, are comparable to the trendline performance of liquid phase epitaxy (LPE)-grown material. The spectral characteristics are similar, with a slight decrease in quantum efficiency attributable to the Si substrate. With respect to R 0 A, the HgCdTe/Si devices are closer to the theoretical radiative-limit than LPE-grown detectors. Known defect densities in the material have been correlated to device performance through a simple model. Slight 1/f noise increases were measured in comparison to the LPE material, but the observed levels are not sufficient to significantly degrade focal plane array (FPA) performance. In addition to discrete detectors, two FPA formats were fabricated. 128 ¥ 128 FPAs show MWIR sensitivity comparable to mature InSb technology, with pixel operability values in excess of 99%. A 640 ¥ 480 FPA further demonstrates the high-sensitivity and high-operability capabilities of this material.
Molecular beam epitaxy grown long wavelength infrared HgCdTe on Si detector performance
Journal of Electronic Materials, 2005
The use of silicon as a substrate alternative to bulk CdZnTe for epitaxial growth of HgCdTe for infrared (IR) detector applications is attractive because of potential cost savings as a result of the large available sizes and the relatively low cost of silicon substrates. However, the potential benefits of silicon as a substrate have been difficult to realize because of the technical challenges of growing low defect density HgCdTe on silicon where the lattice mismatch is ϳ19%. This is especially true for LWIR HgCdTe detectors where the performance can be limited by the high (ϳ5 ϫ 10 6 cm Ϫ2) dislocation density typically found in HgCdTe grown on silicon. We have fabricated a series of long wavelength infrared (LWIR) HgCdTe diodes and several LWIR focal plane arrays (FPAs) with HgCdTe grown on silicon substrates using MBE grown CdTe and CdSeTe buffer layers. The detector arrays were fabricated using Rockwell Scientific's planar diode architecture. The diode and FPA and results at 78 K will be discussed in terms of the high dislocation density (ϳ5 ϫ 10 6 cm 2) typically measured when HgCdTe is grown on silicon substrates.
Molecular Beam Epitaxy Growth of HgCdTe on Large-Area Si and CdZnTe Substrates
Journal of Electronic Materials, 2011
This paper presents the status of HgCdTe growth on large-area Si and CdZnTe substrates at Raytheon Vision Systems (RVS). The different technological tools that were used to scale up the growth from 4 inch to 6 inch diameter on Si and from 4 cm 9 4 cm to 8 cm 9 8 cm on CdZnTe without sacrificing the quality of the layers are described. Extremely high compositional uniformity and low macrodefect density were achieved for single-and two-color HgCdTe layers on both Si and CdZnTe substrates. Finally, a few examples of detector and focal-plane array results are included to highlight the importance of high compositional uniformity and uniformly low macrodefect density of the epitaxial layers in obtaining high operability and low cluster outages in single-and two-color focal-plane arrays (FPAs).