InGaAs Focal Plane Array Research Articles

Quantum dot-enabled infrared hyperspectral imaging with single-pixel detection.

Near-infrared (NIR) hyperspectral imaging is a powerful technique that enables the capture of three-dimensional (3D) spectra-spatial information within the NIR spectral range, offering a wide array of applications. However, the high cost associated with InGaAs focal plane array (FPA) has impeded the widespread adoption of NIR hyperspectral imaging. Addressing this challenge, in this study, we adopt an alternative approach-single-pixel detection for NIR hyperspectral imaging. Our investigation reveals that single-pixel detection outperforms conventional FPA, delivering a superior signal-to-noise ratio (SNR) for both spectral and imaging reconstruction. To implement this strategy, we leverage self-assembled colloidal quantum dots (CQDs) and a digital micromirror device (DMD) for NIR spectral and spatial information multiplexing, complemented by single-pixel detection for simultaneous spectral and image reconstruction. Our experimental results demonstrate successful NIR hyperspectral imaging with a detection window about 600 nm and an average spectral resolution of 8.6 nm with a pixel resolution of 128 × 128. The resulting spectral and spatial data align well with reference instruments, which validates the effectiveness of our approach. By circumventing the need for expensive and bulky FPA and wavelength selection components, our solution shows promise in advancing affordable and accessible NIR hyperspectral imaging technologies, thereby expanding the range of potential applications.

Ultra-Broadband Ultraviolet-Visible Light-Short Wavelength Infrared InGaAs Focal Plane Arrays via n-InP Contact Layer Removal.

PIN InGaAs short wavelength infrared (SWIR) focal plane array (FPA) detectors have attracted extensive attention due to their high detectivity, high quantum efficiency, room temperature operation, low dark current, and good radiation resistance. Furthermore, InGaAs FPA detectors have wide applications in many fields, such as aviation safety, biomedicine, camouflage recognition, and infrared night vision. Recently, extensive research has been conducted on the extension of the response spectrum from short wavelength infrared (SWIR) to visible light (VIS) through InP substrate removal and reserving the n-InP contact layer. However, there is little research on the absorption of InGaAs detectors in the ultraviolet (UV) band. In this paper, we present an ultra-broadband UV-VIS-SWIR 640 × 512 15 μm InGaAs FPA detector by removing the n-InP contact layer in the active area and reserving the InP contact layer around the pixels for n contact, creating incident light to be directly absorbed by the In0.53Ga0.47As absorption layer. In addition, the optical absorption characteristics of InGaAs infrared detectors with and without an n-InP contact layer are studied theoretically. The test results show that the spectral response is extended to the range of 200-1700 nm. The quantum efficiency is higher than 45% over a broad wavelength range of 300-1650 nm. The operability is up to 99.98%, and the responsivity non-uniformity is 3.28%. The imaging capability of InGaAs FPAs without the n-InP contact layer has also been demonstrated, which proves the feasibility of simultaneous detection for these three bands.

Lightly doped In0.53Ga0.47As/InP SWIR photodetectors with diffusion barrier structure

A diffusion barrier structure is proposed to control the accuracies of the Zinc diffusion velocity and depth for lightly doped short-wave infrared (SWIR) InGaAs planar photodetectors. By employing scanning capacitance microscopy and scanning electron microscopy characterizations, the Zinc diffusion profiles were investigated. The introducing of a moderately doped interlayer effectively tailored the diffusion front with reduced depth. In0.53Ga0.47As/InP PIN photodetectors with different structures were fabricated and characterized. Compared with the typical structure, the barrier detector exhibited a significantly lower dark current as well as an approximately three times higher peak detectivity. These results indicated that the diffusion barrier structure is promising for the fabrication of SWIR InGaAs focal plane arrays with both low capacitance and reduced dark current.

Shortwave Infrared InGaAs Detectors On-Chip Integrated with Subwavelength Polarization Gratings.

Shortwave infrared polarization imaging can increase the contrast of the target to the background to improve the detection system's recognition ability. The division of focal plane polarization indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice due to the advantages of compact structure, real-time imaging, and high stability. However, because of the mismatch between nanostructures and photosensitive pixels as well as the crosstalk among the different polarization directions, the currently reported extinction ratio (ER) of superpixel-polarization-integrated detectors cannot meet the needs of high-quality imaging. In this paper, a 1024 × 4 InGaAs FPA detector on-chip integrated with a linear polarization grating (LPG) was realized and tested. The detector displayed good performance throughout the 0.9-1.7 um band, and the ERs at 1064 nm, 1310 nm and 1550 nm reached up to 22:1, 29:1 and 46:1, respectively. For the crosstalk investigation, the optical simulation of the grating-integrated InGaAs pixel was carried out, and the limitation of the ER was calculated. The result showed that the scattering of incident light in the InP substrate led to the crosstalk. Moreover, the deviation of the actual grating morphology from the designed structure caused a further reduction in the ER.

Design and Fabrication of Broadband InGaAs Detectors Integrated with Nanostructures.

A visible-extended shortwave infrared indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice for reducing the size, weight and power (SWaP) of infrared imaging systems, especially in low-light night vision and other fields that require simultaneous visible and near-infrared light detection. However, the lower quantum efficiency in the visible band has limited the extensive application of the visible-extended InGaAs FPA. Recently, a novel optical metasurface has been considered a solution for a high-performance semiconductor photoelectric device due to its highly controllable property of electromagnetic wave manipulation. Broadband Mie resonator arrays, such as nanocones and nanopillars designed with FDTD methods, were integrated on a back-illuminated InGaAs FPA as an AR metasurface. The visible-extended InGaAs detector was fabricated using substrate removal technology. The nanostructures integrated into the Vis-SWIR InGaAs detectors could realize a 10-20% enhanced quantum efficiency and an 18.8% higher FPA response throughout the wavelength range of 500-1700 nm. Compared with the traditional AR coating, nanostructure integration has advantages, such as broadband high responsivity and omnidirection antireflection, as a promising route for future Vis-SWIR InGaAs detectors with higher image quality.

Noise behaviors of SWIR InxGa1-xAs/InP focal plane arrays as a function of lattice-mismatch degree

A quantitatively investigation on the dark noise behaviors of In0.53Ga0.47As/InP, In0.75Ga0.25As/In0.75Al0.25As/InP and In0.83Ga0.17As/In0.83Al0.17As/InP short-wavelength infrared (SWIR) focal plane arrays (FPAs) with cutoff wavelengths (λc) of 1.7, 2.2 and 2.5 μm, respectively, is presented. Theoretical FPA noise model consisting of the diode thermal noise, the dark current shot noise, the operational transimpedance amplifier (OTA) thermal noise, the 1/f noise, the sample and hold noise of the circuit, and etc. were fully taken into consideration. The results show that the dark noises are mainly composed of the OTA thermal noise of the readout circuit under short integration times (Tint) for all three FPAs. Under long Tint, the thermal noises from the photodiode arrays at 300 K is acting as the primary source for the dark noise of the lattice-matched In0.53Ga0.17As FPA, whereas noises of the lattice-mismatched 2.2 and 2.5 μm FPAs are identified to be mainly comes from the diode thermal noise, the dark current shot noise, and the 1/f noise at 150 and 180 K. In addition, an overall trend that the contribution of the 1/f noise increases significantly even if the junction impedance increases and the dark current decreases by cooling down for the extended wavelength detector, which is related to the existence of high density misfit dislocation defect-related trap states in the materials. These results suggest that lowering the junction capacitance and increasing the junction resistance are effective routes to suppress the total readout noise of the InGaAs FPAs, which essentially relies on the improvements on the material epitaxial growth and photodiode array processing recipes.Index Terms: readout noise, lattice-mismatch, focal plane array, InGaAs, noise model.

Corrections to “2.45-μm 1280 × 1024 InGaAs Focal Plane Array With 15-μm Pitch for Extended SWIR Imaging” [Feb 15 2022 231-234

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InGaAs focal plane array for transient astronomy in the NIR

An indium-gallium-arsenide (InGaAs) detector is tested for use on the new Dynamic REd All-sky Monitoring Survey (DREAMS) 0.5-m telescope. DREAMS is novel for its use of InGaAs as a higher-noise and lower-cost alternative to mercury-cadmium-telluride. The Princeton Infrared Technologies 1280SCICAM, which has one of the smallest pitches and largest focal planes of any commercially available InGaAs detector, is extensively characterized to determine the viability of InGaAs detectors for astronomy. We find the 1280SCICAM to have the one of the lowest dark currents (67e − / s) of any commercially available InGaAs focal plane array, and also confirm no fringing or non-linearity is present. Given its low noise, we conclude that DREAMS will be sufficiently background limited with InGaAs, and by extension, InGaAs is well-suited for application on low-angular-resolution NIR instruments.

Study of Residual-time-counting Pulse Frequency Modulation Digital Readout Circuit for Ingaas Focal Plane Array

Study of Residual-time-counting Pulse Frequency Modulation Digital Readout Circuit for Ingaas Focal Plane Array

Ultra-low spectral reflectances of InP Mie resonators on an InGaAs/InP focal plane array

Numerical investigations of an InGaAs/InP focal plane array (FPA) integrated with periodic InP nanostructures are reported. It has been found that column-shape textured FPAs exhibit reflectances of ≤1% over the entire response range of 900 nm–1700 nm. Meanwhile, incident angle-dependent behaviors of the spectral reflectances have been observed. Numerical calculations reveal that such ultra-low reflection characteristics originate from the overlapping of the magnetic and the electric dipole resonances. The optimized structure design of InP nanosphere Mie resonators for minimum backscattering at different wavelengths is also applicable for nano-antennas, introducing a promising route to improve the performance of short wavelength infrared InGaAs FPAs.

Design and fabrication of an InGaAs focal plane array integrated with linear-array polarization grating.

Polarization imaging plays a crucial role in modern photonic applications such as remote sensing, material classification, and reconnaissance. A novel InGaAs focal plane array integrated with linear-array polarization grating is proposed and fabricated to meet the practical needs of near-infrared polarization imaging. In order to accurately evaluate the polarization performance of a fabricated detector, the improved test system is used to measure the transmittance and extinction ratio (ER). The results show that the detectivity reaches ${1}.{06}\; \times \;{{10}^{12}}\;{{\rm cm}\cdot{\rm Hz}^{1/2}}/{\rm W}$1.06×1012cm⋅Hz1/2/W, and the operable pixel factor is more than 99.8%. The transmittance of more than 55% and the ER of greater than 21:1 are realized, which indicates that the fabricated detector has excellent capability for near-infrared polarization imaging.

Characterization and calibration of blind pixels in short-wave infrared InGaAs focal plane arrays

Blind pixels are an inevitable problem in short-wave infrared (SWIR) InGaAs focal plane arrays (FPAs). An experiment using a laser beam-induced current method was set up to characterize the blind pixels in InGaAs FPAs. According to the result, the blind pixels are classified into four types: single overhot pixels, single dead pixels, crossing dead pixels, and paired blind pixels. Additionally, the causes of the different types of blind pixels are analyzed. It is indicated that the blind pixels are caused by defects and impurities, disconnection of the readout circuit, unformed PN junctions, and a wrong connection between the PN junction and readout integrated circuit, respectively. Based on the characterization, a blind pixel calibration method that greatly improved the quality of images taken by InGaAs FPAs is proposed.

Research on polarization performance of InGaAs focal plane array integrated with superpixel-structured subwavelength grating.

Polarization imaging has become a widely-applied detection technique, due to the capabilities of enhanced image contrast and object recognition. Here, we demonstrate 320 × 256 InGaAs focal plane array (FPA) integrated with superpixel-structured subwavelength aluminum grating. An extinction ratio of up to 19:1 at 1310 nm is realized, which indicates a good capability of near-infrared polarization detection. Theoretical simulation shows a fairly high extinction ratio for such superpixel structure. This difference between the actual extinction ratio and the theoretical extinction ratio is further discussed by analyzing the effects of the alignment deviation and structural parameter deviations induced during the actual process. Moreover, the imaging results show that the fabricated polarimetric InGaAs FPA presents a more obvious profile for artificial objects, compared to the conventional detector. Such FPAs integrated with superpixel-structured grating are very promising for high performance polarization imaging in the short wavelength infrared band.

微型近红外物联网节点的传感器输出数字化应用研究

The rise of the Internet of Things (IOT) spectral analysis technology has driven the development of near infrared spectroscopy sensors toward miniaturization, digitization and intelligence. A specific digitization research on InGaAs spectral sensor was reported to meet the digital and intelligent development of InGaAs focal plane Arrays (FPA). A new compact near infrared spectral node was developed integratedly with digital output spectral sensor circuit using self-developed analog to digital convertor (ADC) chip. The proposed node integrated 202 effective spectral channels with a wavelength range of 900 nm to 1 700 nm and a spectral resolution better than 16 nm. The wavelength accuracy and repeatability was less than 1 nm and 0.3 nm, respectively. The signal to noise ratio (SNR) of node system was about 500:1, and the frame scanning time was about 3 ms. The research results show that the compact IOT spectral node meets the practical application requirements of near infrared spectral analysis, and provides technical supports for the sensor on-chip digitization and IOT near infrared spectral analysis applications.

Noise characteristics of short wave infrared InGaAs focal plane arrays

Noise characteristics of short wave infrared InGaAs focal plane arrays

Design of a CMOS ROIC for InGaAs Self-Mixing Detectors Used in FM/cw LADAR

A scannerless laser detection and ranging (LADAR) system based on frequency modulation/continuous wave (FM/cw) technique is attractive due to a reduced bandwidth requirement of the receiver circuit. This paper presents the $64\times 64$ InGaAs-based focal plane array (FPA) self-mixing detectors and the $1\times 32$ element readout integrated circuit (ROIC) array based on transimpedance amplifier for the FM/cw LADAR. Different from conventional detector, the InGaAs self-mixing detector presents a low impedance and a complex electrical model. The linear chirp local-oscillator (LO) electrical signal through the detector causes a large dc current and a unique dc offset voltage (Vos) error in the ROIC. To overcome these problems, the blocking capacitors and the novel multiple low-pass filters are applied in the ROIC. The ROIC array was fabricated in 0.18- $\mu \text{m}$ CMOS process. The measured results show that the Vos error is eliminated within the limited LO amplitude range and the ROIC achieves a 140-dB $\Omega$ transimpedance gain with a bandwidth of 1 MHz. Compared with the state-of-the-art FM/cw LADAR, the ROIC accurately detects the signal of interest of the InGaAs FPA self-mixing detectors and miniaturizes the LADAR receiver.

Numerical simulation of the modulation transfer function in planar InGaAs dense arrays

Three-dimensional simulation methodology has been used to evaluate the performance of lattice matched InGaAs/InP double layer planar heterointerface detector arrays. The device characteristics under optical illumination and dark conditions have been computed. The modulation transfer function (MTF) profiles have been calculated with varying device geometries and carrier dynamics. It is found that the p well diffusion radius and minority carrier recombination play important roles in the MTF behaviors of dense arrays. Moderate p well diffusion dimension should be used to balance the device performances between the dark current and MTF profile. Moreover, better MTF characteristic under low light condition can be achieved with higher quality material which has longer recombination lifetime. The influences of underlying mechanisms including photon generated carriers diffusion and carrier recombination processes have been discussed. These simulation methods and results should provide a useful tool for the evaluation and improvement of imaging power of InGaAs focal plane arrays.

Noise characteristics analysis of short wave infrared InGaAs focal plane arrays

The increasing application of InGaAs short wave infrared (SWIR) focal plane arrays (FPAs) in low light level imaging requires ultra-low noise FPAs. This paper presents the theoretical analysis of FPA noise, and point out that both dark current and detector capacitance strongly affect the FPA noise. The impact of dark current and detector capacitance on FPA noise is compared in different situations. In order to obtain low noise performance FPAs, the demand for reducing detector capacitance is higher especially when pixel pitch is smaller, integration time is shorter, and integration capacitance is larger. Several InGaAs FPAs were measured and analyzed, the experiments’ results could be well fitted to the calculated results. The study found that the major contributor of FPA noise is coupled noise with shorter integration time. The influence of detector capacitance on FPA noise is more significant than that of dark current. To investigate the effect of detector performance on FPA noise, two kinds of photodiodes with different concentration of the absorption layer were fabricated. The detectors’ performance and noise characteristics were measured and analyzed, the results are consistent with that of theoretical analysis.

Very Wide Dynamic Range ROIC With Pixel-Level ADC for SWIR FPAs

This paper describes a new wide dynamic range readout circuit incorporating a pixel-level time-to-digital analog-to-digital converter for a short-wavelength infrared InGaAs focal plane array. To extend the dynamic range, the self-controlled integration capacitance technique and the detector current adaptive integration time technique are adopted in the readout circuit, which is operated individually in each pixel. Each pixel can have an appropriate gain independently depending on the signal current without any help from a digital processor. The readout circuit was fabricated using a 0.35- $\mu \text{m}$ standard CMOS process. The measured results of the fabricated chip show that the dynamic range exceeds 140 dB and that the noise level is 73.35 e-rms.

The development of InGaAs short wavelength infrared focal plane arrays with high performance

High performance, various specifications InGaAs focal plane arrays(FPAs) were studied in Shanghai Institute of Technical Physics (SITP). On the one hand, the typical linear 256×1, 512×1 and 1024×1 FPAs were obtained for response wavelengths from 0.9μm to 1.7μm. The typical 320×256 FPAs and special sizes 512×128, 512×256 FPAs for the near infrared multi-spectral imaging were studied. The performance of InGaAs FPAs from 0.9μm to 1.7μm has improved enormously. The average peak detectivity, the response non-uniformity and non-operable pixel of the FPAs are superior to 3×1012cmHz1/2/W, 5% and 1% at the room temperature. On the other hand, the development of the extended InGaAs FPAs was also focused in SITP. The dark current of InGaAs detectors with the response wavelength from 1.0μm to 2.5μm decreases to about 10nA/cm2 at 200K. The dark current mechanisms for extended InGaAs detectors were studied by P/A photodiodes. The special sizes 512×256 FPAs has been fabricated since 2011. The average peak detectivity, the response non-uniformity and non-operable pixel of the FPAs are superior to 5×1011cmHz1/2/W, 8% and 2% at 200K. In order to verify the performance of FPAs, the short wavelength infrared lens was used to form optical imaging system. The buildings, water, trees are sharply imaged by 320×256 FPAs with 0.9–1.7μm wavelength and 512×1 FPAs with 0.9–2.5μm wavelength at about hundreds of meters distance as target at daylight.