HgCdTe heterostructures on Si(310) substrates for infrared photodetectors (original) (raw)
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HgCdTe heterostructures on Si (310) substrates for midinfrared focal plane arrays
Semiconductors, 2011
Results of studies of the molecular beam epitaxial growth of HgCdTe alloys on Si substrates as large as 100 mm in diameter are presented. Optimum conditions for obtaining HgCdTe/Si(310) heterostruc tures of the device quality for the spectral range of 3-5 μm are determined. The results of measurements and discussion of photoelectric parameters of an infrared photodetector of a format of 320 × 256 elements with a step of 30 μm based on a hybrid assembly of a matrix photosensitive cell with a Si multiplexer are presented. A high stability of photodetector parameters to thermocycling from room temperature to liquid nitrogen temperature is shown.
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.
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/Si materials for long wavelength infrared detectors
Journal of Electronic Materials, 2004
The heteroepitaxial growth of HgCdTe on large-area Si substrates is an enabling technology leading to the production of low-cost, large-format infrared focal plane arrays (FPAs). This approach will allow HgCdTe FPA technology to be scaled beyond the limitations of bulk CdZnTe substrates. We have already achieved excellent mid-wavelength infrared (MWIR) and short wavelength infrared (SWIR) detector and FPA results using HgCdTe grown on 4-in. Si substrates using molecular beam epitaxy (MBE), and this work was focused on extending these results into the long wavelength infrared (LWIR) spectral regime. A series of nine p-on-n LWIR HgCdTe double-layer heterojunction (DLHJ) detector structures were grown on 4-in. Si substrates. The HgCdTe composition uniformity was very good over the entire 4-in. wafer with a typical maximum nonuniformity of 2.2% at the very edge of the wafer; run-to-run composition reproducibility, realized with real-time feedback control using spectroscopic ellipsometry, was also very good. Both secondary ion mass spectrometry (SIMS) and Hall-effect measurements showed well-behaved doping and majority carrier properties, respectively. Preliminary detector results were promising for this initial work and good broad-band spectral response was demonstrated; 61% quantum efficiency was measured, which is very good compared to a maximum allowed value of 70% for a non-antireflection-coated Si surface. The R 0 A products for HgCdTe/Si detectors in the 9.6-µm and 12-µm cutoff range were at least one order of magnitude below typical results for detectors fabricated on bulk CdZnTe substrates. This lower performance was attributed to an elevated dislocation density, which is in the mid-10 6 cm Ϫ2 range. The dislocation density in HgCdTe/Si needs to be reduced to Ͻ10 6 cm Ϫ2 to make high-performance LWIR detectors, and multiple approaches are being tried across the infrared community to achieve this result because the technological payoff is significant.
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.
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.
Progress in MOCVD growth of HgCdTe heterostructures for uncooled infrared photodetectors
Infrared Physics & Technology, 2007
In the paper recent progress at VIGO/MUT (Military University of Technology) MOCVD Laboratory in the growth of Hg 1−x Cd x Te (HgCdTe) multilayer heterostructures on GaAs/CdTe substrates is presented. The optimum conditions for the growth of single layers and complex multilayer heterostructures have been established. One of the crucial stages of HgCdTe epitaxy is CdTe nucleation on GaAs substrate. Successful composite substrates have been obtained with suitable substrate preparation, liner and susceptor treatment, proper control of background fluxes and appropriate nucleation conditions. The other critical stage is the interdiffused multilayer process (IMP). The growth of device-quality HgCdTe heterostructures requires complete homogenization of CdTe-HgTe pairs preserving at the same time suitable sharpness of composition and doping profiles. This requires for IMP pairs to be very thin and grown in a short time.
Growth of MOCVD HgCdTe heterostructures for uncooled infrared photodetectors
Bulletin of The Polish Academy of Sciences-technical Sciences, 2005
In the paper recent progress at VIGO/MUT (Military University of Technology) MOCVD Laboratory in the growth of Hg1−xCdxTe (HgCdTe) multilayer heterostructures on GaAs/CdTe substrates is presented. The optimum conditions for the growth of single layers and complex multilayer heterostructures have been established. One of the crucial stages of HgCdTe epitaxy is CdTe nucleation on GaAs substrate. Successful composite substrates have been obtained with suitable substrate preparation, liner and susceptor treatment, proper control of background fluxes and appropriate nucleation conditions. The other critical stage is the interdiffused multilayer process (IMP). The growth of device-quality HgCdTe heterostructures requires complete homogenization of CdTe-HgTe pairs preserving at the same time suitable sharpness of composition and doping profiles. This requires for IMP pairs to be very thin and grown in a short time. Arsenic and iodine have been used for acceptor and donor doping. Suitable g...
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).
Nanophotonics and Macrophotonics for Space Environments VII, 2013
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