This paper presents performance of very long wavelength infrared HgCdTe detectors operating at 60K for space surveillance and earth observation applications. Fabricated detector arrays were hybridized to Teledyne’s GeoSnap- 18 1024 x 512 read-out integrated circuit of 18-micron x 18-micron pixel format. This is a capacitive transimpedance amplifier pixel design with high linearity. Detector focal plane arrays are made of Teledyne’s high quality molecular beam epitaxy grown HgCdTe infrared detector materials with detector cut-offs near 13.5 microns at 60K. Key detector performance parameters of high operability with low dark currents, high quantum efficiency was demonstrated. One of the FPA was baked at 70oC under vacuum environment for 42 days; pre- and post-bake performance was compared. Dark current operability increased from 94% to 97% for pixels having dark currents ≤ 1.08E9 e-/s/pxl and noise operability also increased from 91% to 94% for pixels having total dark noise ≤ 815 e-/pxl. Obtained minimum dark current is on the order of 3E7 e-/s/pxl, which is a factor of four lower than the RULE07 for 13.24 microns cut off at 60K.

We propose a monolithic broad multi-wavelength NIR LED device to function as a main analysis and viral infections detection component in clinical biology testing equipment. Area selective Quantum Well Intermixing (QWI) is used to produce miniature size LEDs on a single QW substrate. In this research, SiO2 layers that range between 0nm to 400nm with a 50nm thickness steps over separated regions are deposited to create eight regions of different bandgaps. The thicker the diffusion layer the larger the blue shift. Consequently, eight LEDs that emit light in eight different wavelengths each with its individual contact pad are fabricated. Each LED emits a specific wavelength individually that corresponds to the thickness of the deposited SiO2 layer by injecting electrical current into its contact pad and light emission is collected at a single output. As a result, the device can produce light from a single or multiple LEDs simultaneously. For our research, a simultaneous current injection into all LEDs is required to produce a broad infrared light. The LEDs electroluminescence when current is injected at 37mA results in eight wavelengths of: 797,804, 810, 816, 823, 831, 837, 850nm with an average LED responsivity of ~0.4W/A. A calculated average of the optical output shows a broad infrared spectrum from a single structure that can be easily integrated into modern biological analytical tools.

The Earth radiation budget, a 40-year data record of the balance between solar radiation reaching the Earth and the amount reflected, and emitted from the Earth, is a key climate record for determining whether the Earth is warming or cooling. The need for accurate and cost-effective space-based measurements is driving the technology development of broadband bolometers and linear microbolometer arrays. We describe the performance of microfabricated bolometers and 1 x 32 linear microbolometer arrays developed for this purpose. To accurately measure the total outgoing radiation from 0.3 μm to over 100 μm, consisting of reflected shortwave solar radiation and emitted longwave thermal radiation, a vertically aligned carbon nanotube thermal absorber is incorporated with an electrical substitution heater that provides on-board calibration capabilities. A silicon nitride heat link is used to optimize response time while minimizing noise and the inequivalence between thermal and optical heating. The devices operate at room temperature with noise floors at nW/√Hz or lower at the measurement frequency of 7 Hz. Response times below 10 ms have been demonstrated in closed-loop operation using the electrical heater. Thin film Pt thermistors measure the change in microbolometer temperature. The deposition of the thin film thermistors has been optimized to maximize the temperature coefficient of resistance, which is key to meeting the demanding signal-to-noise requirement of this application.

We present the symmetric counterpart to the solar cell that generates power via the net emission rather than absorption of light. This thermoradiative diode (TRD) has enticing applications in night-sky power generation and waste heat recovery. However, while theoretical limits for night-sky power generation are promising, the current technological limits have not been explored. Here we present the electro-optical characteristics a HgCdTe photodiode in thermoradiative and photovoltaic operation, supported by theoretical calculations that include critical non-radiative processes.

The electrical conductivity, temperature coefficient of resistance (TCR), and electrical low frequency noise in VOx thin films were investigated. The electrical conduction is found to be dominated by Variable Range Hopping (VRH). Phenomenological relations between resistivity, TCR, and low frequency noise were determined for VOx films over a wide range of resistivities. It was observed that both TCR and noise increase monotonically with resistivity, as expected for VRH conduction.

Teledyne Judson Technologies (TJT), a subsidiary of Teledyne Imaging Sensors (TIS), and a TIS team in California have jointly developed a low persistence InGaAs focal plane array (FPA) for use in TIS’s MicroCam SWIR camera. This FPA is built on the Hawaii-1RG (H1RG) read-out integrated circuit (ROIC) which has 1024x1024 pixels with an 18 μm pixel pitch format. Operated at 77 K, the newly developed InGaAs arrays achieve cumulative persistence values of ~0.04-0.08% after 45s of integration. This paper reviews the InGaAs detector design and fabrication processes and FPA test results of low persistence focal plane arrays. The persistence test methodology and test data are also presented. A unique epi-wafer and detector structure was designed to allow for low persistence, low dark current, low bad pixel count, high uniformity, and large reverse bias operation (1.5V). The FPA test data is presented for persistence, dark current, quantum efficiency (QE), and correlated double sampling (CDS) noise, as well as bad pixel count and clusters.

The photon detection efficiencies (PDE) of single photon avalanche diodes (SPADs) are investigated for practical applications such as LiDAR, time-of-flight 3D imaging, fluorescence microscopy, etc. After finding the dark count rate (DCR), radiation from a blackbody source is introduced through a light tube to the SPAD detector. Baffles are used in this tube to prevent light from reflecting off the side of the tube onto the detector. The PDE is then calculated knowing the light incident on the detector, the light detected by the detector, the DCR, and the afterpulsing probability. Measurements for several wavelengths, viz., 500, 615, 808, 900, and 940nm, various blackbody aperture diameters and temperatures, and different baffle diameters are reported. The results are then analyzed to find a range of these parameters that produce consistent results with each other, and compared with manufacturer specifications.

We have successfully tested simultaneously 2.4 Micron Wavelength, Extended InGaAs Photodiodes having diameters of 20, 30, 40, 50, 100, 150, 200, 250, and 290 Micron, coupled with a Single Mode Fiber using 100 MeV/n Carbon (C) Ions up to a cumulative dose of ~40 krad. During irradiation, the devices were maintained at dry ice temperature, reverse biased at 100 mV, and their leakage current was continuously monitored in-situ during the run. After the exposure was completed, all nine devices were monitored for any change in their leakage current at 100 mV and room temperature for several weeks to monitor any annealing effects that may occur. Nine Photodiodes with the above varying diameters were radiated with 100 MeV/n Carbon Ions with a fluence of 10⁶, 10⁷, 10⁸, 10⁹, and 10¹⁰ ions/cm² at each fluence level. At 100 MeV/n the Linear Energy Transfer (LET) of Carbon Ion is ~0.156 MeV-cm²/mg in Extended InGaAs, which is an order magnitude more than Proton (H) and Helium (He) Ions of 100 MeV/n energy. Thus, significant displacement damage is anticipated in the Extended InGaAs Photodiode with 100 MeV/n Carbon Ions with a total fluence of 1 × 1010 ions/cm² . Pre- and Post- radiation results were also measured for: (1) Leakage Current Vs. Voltage for the Extended InGaAs Photodiodes; (2) Responsivity (Quantum Efficiency) in A/W for Photodiodes; and (3) Bandwidth of the Photodiodes. All devices were found to be fully functional at the normal operating conditions and at both dry ice and room temperature. The leakage current increased up to a factor of ~2X at lower bias of 100 mV at the highest fluence of 10¹⁰ ions/cm², but not significantly at higher bias of 2 V. We did not observe any post radiation annealing effect for leakage current at room temperature and 100 mV bias for any of the devices after several weeks of data logging.

Current mid-infrared detection technologies dominating the market are mainly based on group III-V semiconductors. These devices have detection range depending upon the materials and also drawbacks like complex and expensive fabrication process, and incompatibility with CMOS processes. To overcome these complexities, silicon-based photodetectors using low cost approaches offer the excellent alternative. The current commercialized silicon-based detector technologies exhibit detection capabilities up to 1100 nm. Here, we have presented a metal–semiconductor silicon-based detectors showing a wider detection range extending from visible light to mid-infrared region. In this work, we investigate a silicon based Schottky diode photodetectors with a thin Ag film of thickness 10 nm over a silicon substrate for detecting radiation emitted from mid-infrared light source. Using lock-in amplifier for further measurement, not only the quality of signal was increased, the detection range of the device is enhanced up-to 5300 nm, which is far beyond the current limit of silicon-based detectors. Hence, the Schottky device used in this study has the potential to detect radiation up to mid-infrared wavelengths. On the other hand, the relative level of noise generated also increases with wavelength, so the detection signal gets buried. These signals have been successfully extracted and analyzed using the technology of Lock-in Amplifier.

We experimentally demonstrate the free-carrier absorption (FCA)-assisted photodetection using a waveguide-integrated bolometer on the silicon-on-insulator (SOI) platform at the near-infrared range (1520-1620 nm). A heavily-doped silicon (n + Si) plays a role as an efficient light absorption medium, which exploits the mechanism of FCA in Si. For the thermal-to-electrical conversion, a bolometric material of TiOx/Ti/TiOx tri-layer film is integrated onto the n + Si. It offers a sensitivity of -26.75 %/mW with a highly flat spectral response. In addition, a clear on/off bolometric response with the 1 kHz-modulated optical signal was obtained with the rise and fall times of 24.2 μs and 29.2 μs, respectively, which is enough for diverse sensing applications.

Nanostructured antireflection (AR) coatings reducing optical reflections and maximizing radiation transmitted onto the surfaces of substrates, optics and optical devices such as detectors have many potential optical applications over ultraviolet (UV) to infrared (IR) wavebands including for NASA sensor applications. Through nanoengineering optical layers and tuning their refractive indexes, broadband and omnidirectional suppression of light reflection and scattering is achievable with increased optical transmission for enhanced IR detector and system performance over a wide range of light incidence angles. AR nanostructures have been developed that enable the realization of optimal AR coatings with high laser damage thresholds and high reliability in extreme low temperature environments and under launch conditions. These advanced nanostructured AR coatings we have developed and tested on GaSb and IR detector arrays devices primarily for 3-5 and 8-14 µm MWIR/LWIR applications provide substantial improvements over more conventional thin film AR coating technologies such as quarter-wavelength coatings. The growth of step-graded nanostructured layers using a process involving deposition at different tilt angles has produced single-layer AR coatings utilizing ZnS demonstrating below 4% reflectance, compared to ~34% reflectance for uncoated GaSb, across LWIR bands of interest with substantial improvement in quantum efficiency. In this paper we review and present latest developments and testing results for these high-performance nanostructure-based AR coatings for advanced LWIR band NASA Earth Science sensing and imaging applications.

Conventional photodetectors based on HgCdTe material and designed to absorb mid-wave infrared (MWIR) band wavelengths typically require cryogenic or at minimum thermoelectric cooling to maintain adequate levels of infrared (IR) sensing performance. This cooling requirement invariably entails augmentations in size, power, and cost, which for space and satellite applications such as remote sensing and earth observation generally are limiting in scope and potentially prohibitive. Here we report a scalable, low cost, low power, and small footprint room temperature operating MWIR sensing device involving the integration of bilayer graphene functioning as a high mobility channel with HgCdTe material, to limit the recombination of photogenerated carriers and achieve higher performance detection over the 2-5 μm MWIR without the need of an additional cooling mechanism. For the development of these graphene-enhanced HgCdTe MWIR photodetectors, graphene bilayers on Si/SiO2 substrates were doped with boron using a spin-on dopant (SOD) process, and then transferred onto HgCdTe substrates for enhanced higher-mobility photodetection. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and secondary-ion mass spectroscopy (SIMS) were employed to analyze dopant levels and structural properties of the graphene through various stages of the development process and characterize the p-doped graphene following doping and transfer. The features and enhanced performance of the room-temperature operating graphene-based HgCdTe MWIR detectors were demonstrated through modeling, material characterization, and measurements of detector IR sensitivity and response performance.

The advantages of SWIR imaging in comparison to imaging in the VIS range are twofold: At first, the observation range is higher due to a better transmission of the atmosphere especially under hazy weather conditions. At second, the target contrast is higher in many relevant cases caused by a reflection behavior of objects differing significantly from what we know from the visible. In this lecture, a method is presented which, similar to the tristimulus theory of the eye, creates a SWIR image consisting of 4 individual images. The recordings are made with bandpass filters at the wavelengths of 1000 nm, 1200 nm, 1400 nm and 1600 nm. The complete SWIR spectrum is spectrally resolved from the overlap of the filter curves.

Present microbolometer technology for infrared (IR) sensing and imaging has featured microbridges comprising Si3N4 as well as VOx materials and shown decent performance for IR band detection applications. Nevertheless, further integration of carbon nanotubes (CNTs) and graphene can improve the temperature coefficient of resistance (TCR) to provide even higher dynamic range. For the development of high performance and low noise IR microbolometer detectors with improved TCR, vanadium oxide (VOx) layers were grown on 4-inch SiO2/Si wafers as well as on Si substrates using a DC sputtering process with flow of oxygen and argon gases. From energy-dispersive X-ray spectroscopy (EDS) measurements of the sputter-assisted VOx layer growth it was determined that reduced Ar:O flow resulted in lower measured O/V ratios, and therefore more optimal stochiometric properties in the VOx layers. Likewise, analysis of scanning electron microscopy (SEM) images demonstrated that DC sputtering power had a substantial impact on the deposition rates and corresponding VOx layer thickness. Using a gas flow ratio of 18.7:1.3, with DC sputtering powers of approximately 300 W, V/O ratios in the 1.8-1.9 target range and 200 nm target thicknesses, respectively, were achievable in VOx layer growth on SiO2/Si substrates. The electrical and performance properties of these optimized VOx layer test structures were then measured and characterized in view of integration with graphene and single wall and multiwall carbon nanotubes (CNTs) for advanced long-wave infrared (LWIR) detection. These demonstrated significant noise reductions and as well as enhancements in the TCR, indicating the potential for improved noise equivalent temperature difference (NETD) for high imaging cameras and microbolometer focal plane array (FPA) performance for defense and commercial LWIR sensing applications.

For chalcogenide-based infrared glass materials, the need was emphasized along with the spread of thermal imaging cameras in COVID 19 environment. Commercial Ge-As-Se glass system exhibits a dispersion value of 100~180 and a refractive index of 2.5 or more, and is suitable for the glass molding process, so it is used as an aspherical infrared lens for various thermal imaging cameras. However, some compositions are not suitable for glass molding process. In this study, the composition of the long wavelength infrared glass melting was designed based on the Ge-As-Se system with a Ge composition range of 0~35 at%, As composition range of 20~40 at%, and Se composition range of 25~60 at%. As a result of XRD analysis for each Ge-As-Se-based composition, it was confirmed that all amorphous grains were obtained in the developed composition area. For the Ge-As-Se glass-forming composition region, the glass transition temperature ranged from 180 to 425°C. The refractive index was measured using the prism method in the 3 to 12 μm wavelength band. The refractive index (λ=10 μm) of Ge5As40Se55 and Ge5As35Se60 was 2.6913 and 2.6538, respectively. Moldability test was performed using a glass molding press. As a result of observing whether the lens has internal defects and microcracks after molding, it was confirmed that there was no abnormality and that it was suitable for glass molding process.

The electromagnetic spectrum consists of ultraviolet (100-400 nm), visible (400-750 nm), and infrared (750-2500 nm) regions, among others. The visible region contains the wavelengths that can be seen by the human eye, and infrared light is outside the red edge of this band when the light emitted from any source or heating element is spectrally dispersed. In the infrared band, the electromagnetic waves with the shortest wavelength are referred to as near-infrared rays (750-1000 nm). An organic photovoltaic capable of generating light in the near-infrared wavelength band was fabricated herein through bandgap matching of the photoactive polymer for sensing in the near-infrared region. In addition, the organic photovoltaic was optimized through a newly synthesized functional intermediate layer; this layer constitutes a hole-transport layer that transfers the holes generated by the photoactive layer to the cathode easily. The material traditionally used for the hole-transport layer is PEDOT:PSS, which has the advantages of excellent heat resistance as well as high electrical conductivity and transparency. However, PEDOT:PSS also has drawbacks, such as cost inefficiency, strong acidity, and high hydrophilicity. We have synthesized a polypyrrole polystyrene sulfonate (PPY:PSS) as a hole-transport material that overcomes these disadvantages and optimized it by adjusting the ratio of PPY to PSS. Next, poly[4,8- bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4- b]thiophene-)-(2-carboxylate-2-6-diyl)]:phenyl‐C70‐butyric acid methyl ester (PTB7-th:PC70BM) active-layer-based organic photovoltaic was fabricated. Thus, an organic photodiode capable of sensing more effectively in the near-infrared region was developed by inserting the functional interlayer.

This PDF file contains the front matter associated with SPIE Proceedings Volume 12234 including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.