Weather satellite instruments require detectors with a variety of wavelengths ranging from the visible to VLWIR. The Cross-track infrared Sounder (CrIS) is a Polar Orbiting interferometric sensor that measures earth radiances at high spectral resolution, using the data to provide pressure, temperature and moisture profiles of the atmosphere. The pressure, temperature and moisture sounding data are used in weather prediction models that track storms, predict levels of precipitation etc. The CrIS instrument contains SWIR (λc ~ 5 μm at 98 K), MWIR (λc ~ 9 μm at 98 K) and LWIRs (λc ~ 15.4 μm at 81 K) bands in three Focal Plane Array Assemblies (FPAAs). CrIS detectors are 850 μm diameter detectors with each FPAA consisting of nine photovoltaic detectors arranged in a 3 x 3 pattern. Molecular beam epitaxy (MBE)-grown Hg1-xCdxTe material are used for the detectors fabricated in a modified Double Layer Planar Heterostructure (DLPH) architecture. Each detector has an accompanying cold preamplifier. SWIR and MWIR FPAAs operate at 98 K and the LWIR FPAA at 81 K, permitting the use of passive radiators to cool the detectors. D* requirements at peak 14.01 μm wavelength are ≥ 5.0E+10 Jones for LWIR, ≥ 7.5E+10 Jones at 8.26 μm for MWIR and ≥ 3.0E+11 Jones at peak 4.64 μm wavelength for SWIR. All FPAAs exceeded the D* requirements. Measured mean values for the nine photodiodes in each of the LWIR, MWIR and SWIR FPAAs are D* = 5.3 x 1010 cm-Hz1/2/W at 14.0 μm, 9.6 x 1010 cm-Hz1/2/W at 8.0 μm and 3.4 x 1011 cm-Hz1/2/W at 4.64 μm.

The photocurrent of High Density Vertically Integrated Photodiodes (HDVIP) manufactured in LPE grown SWIR (λc ~ 2.5 μm) HgCdTe material is modeled as a function of incident spot location using a Monte Carlo diffusion calculation in the p-type bulk. The Monte Carlo calculation assumes a 3 x 3 mini-array of detectors surrounded by guard detectors. Carriers generated in the n-regions are always collected. The result is a responsivity map that yields the individual detector "spot scan" profile that is then used to calculate the detector modulation transfer function (MTF). Fourier transforms of detector "spot scan" response profile provided experimental confirmation of MTF that corresponded to the Monte Carlo modeled MTF.

DRS uses LPE-grown SWIR, MWIR and LWIR HgCdTe material to fabricate High-Density Vertically Integrated Photodiode (HDVIP) architecture detectors. 2.5 μm, 5.3 μm and 10.5 μm cutoff detectors have been fabricated into linear arrays as technology demonstrations targeting remote sensing programs. This paper presents 320 x 6 array configuration technology demonstrations' performance of HDVIP HgCdTe detectors and single detector noise data. The single detector data are acquired from within the 320 x 6 array. Within the arrays, the detector size is 40 μm x 50 μm. The MWIR detector array has a mean quantum efficiency of 89.2% with a standard deviation to mean ratio, σ/μ = 1.51%. The integration time for the focal plane array (FPA) measurements is 1.76 ms with a frame rate of 557.7 Hz. Operability values exceeding 99.5% have been obtained. The LWIR arrays measured at 60 K had high operability with only ~ 3% of the detectors having out of family response. Using the best detector select (BDS) feature in the read out integrated circuit (ROIC), a feature that picks out the best detector in every row of six detectors, a 320 x 1 array with 100% operability is obtained. For the 320 x 1 array constituted using the BDS feature, a 100% operable LWIR array with average NEI value of 1.94 x 1011 ph/cm 2/s at a flux of 7.0 x 1014 ph/cm2/s has been demonstrated. Noise was measured at 60 K and 50 mV reverse bias on a column of 320 diodes from a 320 x 6 LWIR array. Integration time for the measurement was 1.76 ms. Output voltage for the detectors was sampled every 100th frame. 32,768 frames of time series data were collected for a total record length of 98 minutes. The frame average for a number of detectors was subtracted from each detector to correct for temperature drift and any common-mode noise. The corrected time series data was Fourier transformed to obtain the noise spectral density as a function of frequency. Since the total time for collecting the 32,768 time data series points is 98.0 minutes, the minimum frequency is 170 μHz. A least squares fit of the form (A/f + B) is made to the noise spectral density data to extract coefficients A and B that relate to the 1/f and white noise of the detector respectively. In addition noise measurements were also acquired on columns of SWIR detectors. Measurements were made under illuminated conditions at 4 mV and 50 mV reverse bias and under dark conditions at 50 mV reverse bias. The total collection time for the SWIR detectors was 47.7 minutes. The detectors are white noise limited down to ~10 mHz under dark conditions and down to ~ 100 mHz under illuminated conditions.

Remote sensing programs require detectors with a variety of wavelengths. One example of remote sensing applications is the GOES-ABI program that requires linear arrays of detectors with cutoff wavelengths ranging from the visible to the VLWIR (λc ~ 15 μm). In order to target the variety of remote sensing applications, an internal task was conducted to develop detectors and linear arrays operating under nominal remote sensing applications. SWIR [λc(295 K) ~ 2.5 μm] test detectors have been measured as a function of temperature between 170 K and 295 K. At 200 K the RoA values are in the 106 ohm-cm2 range. MWIR [λc(60 K) = 5.3 μm] and LWIR [λc(60 K) = 10.5 μm] HgCdTe detectors in a 320 x 6 array format have also been measured at 60 K. Within the arrays, the detector size is 40 μm x 50 μm. The MWIR detector array has a mean quantum efficiency of 89.2 % with a standard deviation to mean ratio, σ/μ = 1.51 %. The integration time for the focal plane array (FPA) measurements is 1.76 ms with a frame rate of 557.7 Hz. Operability values exceeding 99.5 % have been obtained. In addition, test diodes at the edge of the array that did not go through a read out integrated circuit (ROIC) were also measured and had quantum efficiency ~ 86 % that agreed well with the ~ 87 % quantum efficiency measured for detectors in the array that were located near the test detectors. The LWIR arrays, measured at 60K also had high operability with only ~ 3 % of the detectors having out of family response. Using best detector select (BDS) feature in the read out integrated circuit (ROIC), a feature that picks out the best detector in every row of six detectors, a 320 x 1 array with 100 % operability is obtained. For the 320 x1 array constituted using the BDS feature, a 100 % operable LWIR array with average NEI value of 1.94x1011 ph/cm2/s at a flux of 7.0x1014 ph/cm2/s has been demonstrated.

In the last few years Rockwell has developed a novel simultaneous unipolar multispectral integrated HgCdTe detector and focal plane array technology that is a natural and relatively straightforward derivative of our baseline double layer planar heterostructure (DLPH) molecular beam epitaxial (MBE) technology. Recently this technology was awarded a U.S. patent. This simultaneous unipolar multispectral integrated technology (SUMIT) shares the high performance characteristics of its DLPH antecedent. Two color focal plane arrays with low-10 13 cm −2 s −1 background limited detectivity performance (BLIP D * ) have been obtained for mid-wave infrared (MWIR, 3–5 m) devices at T>130 K and for long-wave infrared (LWIR, 8–10 m) devices at T∼80 K.

This paper reviews Boeing's progress, over the last three years, in Vanadium Oxide (VOx) uncooled microbolometer focal plane (UFPA) technology and product development. Boeing's UFPA product technology is described, including product capabilities and performance. Focal plane NETD = 31 mK (F/1), at a 30 Hz sensor frame rate, has been demonstrated on the U3000 320x240 UFPA product. At a 60 Hz frame rate, the NETD (F/1) achieved on production U3000 UFPAs is typically < 60 mK, and spatial pattern noise levels are consistently < 33 mK after sensor level gain and offset compensation. Key improvements in VOx thin-film technology have been the achievement of a Temperature Coefficient of Resistance (TCR) 3%, and the achievement of microbolometer resistance uniformity of similar to 1/3% (sigma/mu) on the UFPA die. Looking into the future, this year Boeing expects to achieve NETD similar to 20 mK (F/1) with very low pattern noise, and within the next three years higher density 640x480 focal planes will be demonstrated with essentially equivalent NETD performance. Large high density uncooled LWIR focal planes, combined with low NETD, will make UFPA technology a prime candidate for higher performance FLIR applications.