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Arkun F.E.,Teledyne Imaging Sensors | Edwall D.D.,Teledyne Imaging Sensors | Ellsworth J.,Teledyne Imaging Sensors | Douglas S.,Teledyne Imaging Sensors | And 2 more authors.
Journal of Electronic Materials | Year: 2017

Recent advances in growth of Hg1−xCdxTe films on large-area (7 cm × 7.5 cm) CdZnTe (CZT) substrates is presented. Growth of Hg1−xCdxTe with good uniformity on large-area wafers is achieved using a Riber 412 molecular beam epitaxy (MBE) tool designed for growth of Hg1−xCdxTe compounds. The reactor is equipped with conventional CdTe, Te, and Hg sources for achieving uniform exposure of the wafer during growth. The composition of the Hg1−xCdxTe compound is controlled in situ by employing a closed-loop spectral ellipsometry technique to achieve a cutoff wavelength (λco) of 14 μm at 78 K. We present data on the thickness and composition uniformity of films grown for large-format focal-plane array applications. The composition and thickness nonuniformity are determined to be <1% over the area of a 7 cm × 7.5 cm wafer. The films are further characterized by Fourier-transform infrared spectroscopy, optical microscopy, and Hall measurements. Additionally, defect maps show the spatial distribution of defects generated during the epitaxial growth of the Hg1−xCdxTe films. Microdefect densities are in the low 103 cm−2 range, and void defects are below 500 cm−2. Dislocation densities less than 5 × 105 cm−2 are routinely achieved for Hg1−xCdxTe films grown on CZT substrates. HgCdTe 4k × 4k focal-plane arrays with 15 μm pitch for astronomical wide-area infrared imagers have been produced using the recently developed MBE growth process at Teledyne Imaging Sensors. © 2017 The Minerals, Metals & Materials Society


Billman C.A.,U.S. Army | Almeida L.A.,U.S. Army | Smith P.,U.S. Army | Arias J.M.,U.S. Army | And 3 more authors.
Journal of Electronic Materials | Year: 2011

The effects of microvoid defects on the performance of mid-wavelength infrared (MWIR) HgCdTe-based diodes were examined. Molecular beam epitaxy (MBE) was utilized to deposit indium-doped, Hg 0.68Cd 0.32Te on 2 cm × 3 cm, (211)B-oriented, bulk Cd 0.96Zn 0.04Te substrates. These epilayers generally exhibited state-of-the-art material properties with a notable exception: high and nonuniform microvoid defect densities (mid 10 4 cm -2 to low 10 6 cm -2). Diodes were fabricated by ion implantation of arsenic to form planar p-n junctions. Dark current-voltage (I-V) curves were measured and analyzed as a function of operating temperature. There was an inverse correlation between wafer-level microvoid defect density and device operability. On each wafer, devices with the smallest implants exhibited higher operability than devices with larger implants. By removal of pad metal and examination of defects within each implant area, it was found that the presence of one or more microvoids within the junction usually caused tunneling or other high-current mechanisms. Diodes free from microvoids exhibited diffusion-limited behavior down to 150 K, the test set limit. © 2011 TMS (outside the USA).


Stoltz A.J.,U.S. Army | Benson J.D.,U.S. Army | Carmody M.,Teledyne Imaging Sensors | Farrell S.,U.S. Army | And 4 more authors.
Journal of Electronic Materials | Year: 2011

HgCdTe, because of its narrow band gap and low dark current, is the infrared detector material of choice for several military and commercial applications. CdZnTe is the substrate of choice for HgCdTe as it can be lattice matched, resulting in low-defect-density epitaxy. Being often small and not circular, layers grown on CdZnTe are difficult to process in standard semiconductor equipment. Furthermore, CdZnTe can often be very expensive. Alternative inexpensive large circular substrates, such as silicon or gallium arsenide, are needed to scale production of HgCdTe detectors. Growth of HgCdTe on these alternative substrates has its own difficulty, namely a large lattice mismatch (19% for Si and 14% for GaAs). This large mismatch results in high defect density and reduced detector performance. In this paper we discuss ways to reduce the effects of dislocations by gettering these defects to the edge of a reticulated structure. These reticulated surfaces enable stress-free regions for dislocations to glide to. In the work described herein, HgCdTe-on-Si diodes have been produced with R 0 A 0 of over 400 Ω cm 2 at 78 K and cutoff of 10.1 μm. Further, these diodes have good uniformity at 78 K at both 9.3 μm and 10.14 μm. © 2011 TMS (outside the USA).


Aifer E.H.,U.S. Navy | Warner J.H.,U.S. Navy | Canedy C.L.,U.S. Navy | Vurgaftman I.,U.S. Navy | And 6 more authors.
Journal of Electronic Materials | Year: 2010

Shallow-etch mesa isolation (SEMI) of graded-bandgap "W"- structured type II superlattice (GGW) infrared photodiodes provides a powerful means for reducing excess dark currents due to surface and bulk junction related processes, and it is particularly well suited for focal-plane array fabrication. In the n-on-p GGW photodiode structure the energy gap is increased in a series of steps from that of the lightly p-type infrared-absorbing region to a value typically two to three times larger. The wider gap levels off about 10 nm short of the doping defined junction, and continues for another 0.25 μm into the heavily n-doped cathode before the structure is terminated by an n+-doped InAs top cap layer. The increased bandgap in the high-field region near the junction helps to strongly suppress both bulk tunneling and generation-recombination (G-R) current by imposing a much larger tunneling barrier and exponentially lowering the intrinsic carrier concentration. The SEMI approach takes further advantage of the graded structure by exposing only the widest-gap layers on etched surfaces. This lowers surface recombination and trap-assisted tunneling in much the same way as the GGW suppresses these processes in the bulk. Using SEMI, individual photodiodes are defined using a shallow etch that typically terminates only 10 nm to 20 nm past the junction, which is sufficient to isolate neighboring pixels while leaving the narrow-gap absorber layer buried 100 nm to 200 nm below the surface. This provides for separate optimization of the photodiode's electrical and optical area. The area of the junction can be reduced to a fraction of that of the pixel, lowering bulk junction current, while maintaining 100% optical fill factor with the undisturbed absorber layer. Finally, with the elimination of deep, high-aspect-ratio trenches, SEMI simplifies array fabrication. We report herein results from SEMI-processed GGW devices, including large-area discrete photodiodes, mini-arrays, and a focal-plane array. Current-voltage data show strong suppression of side-wall leakage relative to that for more deeply etched devices, as well as scaling of dark current with junction area without loss of quantum efficiency. © 2010 U. S. Naval Research Laboratory Department of the Navy.


Grein C.H.,Episensors, Inc. | Grein C.H.,University of Illinois at Chicago | Flatte M.E.,Episensors, Inc. | Flatte M.E.,University of Iowa | And 4 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2013

Type-II strained layer superlattices (SLSs) offer a broad range of design degrees of freedom to help optimize their properties as absorber layers of infrared photon detectors. We theoretically examine a new class of mid-wavelength infrared (2-5 μm bandpass) Type-II structures with two-layer InGaSb/InPSb and four-layer InAs/GaSb/InAs/InPSb SLS periods. Phosphorous-containing SLSs are a promising approach to improving infrared photon detector performance due to providing a new set of material properties, including favorable valence band offsets. P-based SLSs of four-layer type InAs/GaSb/InAs/InPSb were found to be among the best 5-μm gap SLSs that we have modeled. Among the studied designs, the lowest dark current in an ideal structure is predicted for a four-layer 23.6 Å InAs/20 Å GaSb/23.6 Å InAs/60 Å InP0.62Sb0.38 SLS. Its predicted ideal dark current is about 35 times lower than an n-type HgCdTe-based photodiode absorber and six times lower than a p-type HgCdTe one for the same bandgap, temperature, and dopant concentration. We also discuss a defect mitigation strategy that involves positioning the SLS gap in an energy range that avoids defect levels and show how this applies to the aforementioned P-containing SLS. © 1995-2012 IEEE.


Vurgaftman I.,U.S. Navy | Canedy C.L.,U.S. Navy | Jackson E.M.,U.S. Navy | Nolde J.A.,U.S. Navy | And 6 more authors.
Optical Engineering | Year: 2011

We discuss the current performance of long-wavelength infrared photodetectors based on type-II superlattices, and the projected characteristics for diffusion-limited operation. For optimized architectures such as graded-gap and abrupt-heterojunction designs, the dark currents are strongly dominated by Shockley-Read (SR) rather than Auger processes. A factor of 10 improvement over the demonstrated SR lifetimes would lead to a factor of 4 lower dark current than state-of-the-art HgCdTe devices. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).


Piquette E.C.,Teledyne Imaging Sensors | McLevige W.,Teledyne Imaging Sensors | Auyeung J.,Teledyne Imaging Sensors | Wong A.,Teledyne Imaging Sensors
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We describe progress in the development and demonstration of Teledyne's new high resolution large format FPA for astronomy, the H4RG-10 IR. The H4RG-10 is the latest in Teledyne's H×RG line of sensors, in a 4096×4096 format using 10 micron pixels. It is offered as a hybrid sensor using either a silicon p-i-n detector array (HyViSI) or a HgCdTe photodiode array with standard infrared cutoff wavelength of 1.75μm, 2.5μm, or 5.3μm (with custom cutoff wavelengths also available). The HgCdTe sensor arrays are fully substrate removed to provide high quantum efficiency, response to visible wavelengths, and minimize cosmic ray and fringing mitigation. Packaging using either CE6 or SiC bases is available. Teledyne is currently fabricating H4RG-10 SWIR FPAs for NASA's WFIRST space telescope instrument. Initial array performance has been tested and will be presented. Key results include the demonstration of low dark current (array mean dark current of <0.01e-/s/pixel at 100K), low noise (<10 e-/CDS read noise), and high array operability (>99% pixels). The paper discusses the sensor configuration and features, the performance achieved to date including QE, dark current, noise maps and histograms, and the remaining challenges. © 2014 SPIE.


Hood A.D.,Teledyne Imaging Sensors | Evans A.J.,Teledyne Imaging Sensors | Ikhlassi A.,Teledyne Imaging Sensors | Lee D.L.,Teledyne Imaging Sensors | Tennant W.E.,Teledyne Imaging Sensors
Journal of Electronic Materials | Year: 2010

Strained-layer superlattices (SLS) based on type II InAs/Ga(In)Sb materials are a rapidly maturing technology and are theoretically predicted to exceed the dark-current performance of state-of-the-art HgCdTe. A substantial effort is underway at Teledyne Imaging Sensors in the development of SLS materials for infrared focal-plane arrays. In this paper, we describe state-of-the-art materials, device research and characterization, along with testing results for long-wavelength infrared SLS devices based on double-heterostructure and p+-B-n architectures, having n-on-p and p-on-n polarities, respectively. Detector materials exhibited excellent morphological and crystalline characteristics, and electro-optical characterization demonstrated performance comparable to the state of the art. © 2010 TMS.


Tennant W.E.,Teledyne Imaging Sensors
Journal of Electronic Materials | Year: 2010

"Rule 07" was proposed 2 years ago as a convenient rule of thumb to estimate the dark current density for state-of-the-art planar, ion-implanted, p/n HgCdTe photodiodes fabricated in layers grown by molecular-beam epitaxy (MBE). The best reported HgCdTe devices from other laboratories had dark currents no lower than the rule and often higher. In the intervening time we have continued to compare the rule with performance obtained by ourselves and others to see if it stands the test of time. We also examined why it succeeds in approximating the dark current density over the thermal infrared wavebands (>4.6 μm cutoff). It turns out that the rule has held up well, still predicting dark current density values within 0.4× to 2.5× over about 13 orders of magnitude. At least at mid-wavelength infrared-long- wavelength infrared wavelengths, where the dependence is exponential with inverse cutoff and temperature, the behavior can be explained by Auger 1 processes and the diode architecture. This has significant implications for high-operating-temperature devices. Copyright; © 2010 TMS.


Tennant W.E.,Teledyne Imaging Sensors
Progress in Quantum Electronics | Year: 2012

This paper analyses the electro-optical behavior of simple, near-optimal MWIR HgCdTe photodiodes. These devices operate near fundamental materials limits making them both excellent in quality and ideal for understanding the most basic aspects of infrared photodiode performance. Measurements of representative diodes are explained by models that are simple but still accurate in describing optical and electrical properties. © 2012 Elsevier Ltd.

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