Image Sensor Applications Research Articles

Systematic Investigation on Deposition Temperature Effect of Ni1–xO Thin Films for Uncooled Infrared Image Sensor Applications

Nickel oxide (Ni1– x O) films deposited by RF reactive magnetron sputtering were investigated at various substrate temperatures ranging from room temperature to 250 °C for uncooled infrared image sensor applications. The structural properties measured by X-ray diffraction and X-ray photoelectron spectroscopy showed that the deposited films had a Ni-deficient structure and that films deposited at a higher temperature showed more crystallized structures with fewer microstructural defects. These defects had an effect on several properties influencing the sensing performance. The conductivity was found to decrease from 9.47 to 0.10 S/cm with the deposition temperature. In addition, with an increase in the deposition temperature, both the absolute temperature coefficient of resistance and the normalized Hooge parameter, representing the magnitude of 1/ $f$ noise, increased from 1.56%/K to 2.76%/K and from $9.12\times 10^{\mathrm {-28}}$ to $2.40\times 10^{\mathrm {-27}}~\text{m}^{\mathrm {3}}$ , respectively. ( $\alpha _{{H}}$ /n) $^{\mathrm {1/2}}/\vert \beta \vert $ , a useful figure of merit determining the performance of infrared sensor, was varied in the range of $1.77\times 10^{\mathrm {-14}}$ and $2.06\times 10^{\mathrm {-14}}~\text{m}^{\mathrm {3/2}}\text{K}$ /% with the deposition temperature, and the best performance was obtained from the film deposited at 250 °C. Consequently, the nickel oxide film is deemed to be a good potential candidate for uncooled infrared sensor applications.

Low dark current inverted organic photodetectors employing MoOx:Al cathode interlayer

Abstract We report low dark current small molecule organic photodetectors (OPDs) with an inverted geometry for image sensor applications. Adopting a very thin MoOx:Al cathode interlayer (CIL) in the inverted OPD with a reflective top electrode results in a remarkably low dark current density (Jd) of 5.6 nA/cm2 at reverse bias of 3 V, while maintaining high external quantum efficiency (EQE) of 56.1% at visible wavelengths. The effectiveness of the CIL on the diode performance has been further identified by application to inverted OPDs with a semi-transparent top electrode, leading to a significantly low Jd of 0.25 nA/cm2, moderately high EQE540 nm of 25.8%, and subsequently high detectivity of 8.95 × 1012 Jones at reverse bias of 3 V. Possible origins of reduced dark currents in the OPD by using the MoOx:Al CIL are further described in terms of the change of interfacial energy barrier and surface morphology.

A Negative Index Metamaterial-Inspired UWB Antenna with an Integration of Complementary SRR and CLS Unit Cells for Microwave Imaging Sensor Applications.

This paper presents a negative index metamaterial incorporated UWB antenna with an integration of complementary SRR (split-ring resonator) and CLS (capacitive loaded strip) unit cells for microwave imaging sensor applications. This metamaterial UWB antenna sensor consists of four unit cells along one axis, where each unit cell incorporates a complementary SRR and CLS pair. This integration enables a design layout that allows both a negative value of permittivity and a negative value of permeability simultaneous, resulting in a durable negative index to enhance the antenna sensor performance for microwave imaging sensor applications. The proposed MTM antenna sensor was designed and fabricated on an FR4 substrate having a thickness of 1.6 mm and a dielectric constant of 4.6. The electrical dimensions of this antenna sensor are 0.20 λ × 0.29 λ at a lower frequency of 3.1 GHz. This antenna sensor achieves a 131.5% bandwidth (VSWR < 2) covering the frequency bands from 3.1 GHz to more than 15 GHz with a maximum gain of 6.57 dBi. High fidelity factor and gain, smooth surface-current distribution and nearly omni-directional radiation patterns with low cross-polarization confirm that the proposed negative index UWB antenna is a promising entrant in the field of microwave imaging sensors.

(Invited) Considerations for Materials, Processes, and Characterization of Flexible Electronics

Conventional methods of monolithic integration are reaching a practical limit for large-area electronics where miniaturization is not the major constraint for scaling the technology. An overview of novel printing approaches to fabricate thin-film transistors (TFTs) on flexible polymeric substrates for displays and image sensor applications will be presented. The effect of low-temperature processing of Si-based device characteristics will be discussed along with long-term device stability of organic and inorganic semiconductor TFTs under both electrical bias and mechanical strain. Finally, a comparison of the advantages and disadvantages between organic/polymeric and Si-based semiconductor devices on flexible platforms will be reviewed.

A Pump-Gate Jot Device With High Conversion Gain for a Quanta Image Sensor

A new photodetector designed for Quanta image sensor application is proposed. The photodetector is a backside-illuminated, buried photodiode with a vertically integrated pump and transfer gate and a distal floating diffusion to reduce parasitic capacitance. The structure features compact layout and high conversion gain. The proposed device is modeled and simulated, and its performance characteristics estimated.

Application of Simple Multispectral Image Sensor and Artificial Intelligence for Predicting of Drought Tolerant Variety of Soybean

Environmental stress such as drought is a limiting factor of the soybean production in Indonesia. The varieties of drought- tolerant soybean become necessary to be cultivated especially in a marginal farmland. The characteristics of these varieties can be identified from the morphology of plants and the content of chlorophylls. Conventional techniques for predicting the variety of drought tolerant are usually labor extensive, time consuming and costly. A simple and rapid method that based on an automatic system to provide predictions on the variety of drought tolerant soybean is proposed in this paper. The method uses a simple multispectral sensor from a web camera that captures physical and physiological characteristics such as leaf areas, plant heights and is also able to calculate the content of chlorophylls. This research also compared fuzzy logic and artificial neural network as artificial intelligence methods to process raw data in order to predict the variety of the drought resistance soybean. The drought tolerant variety can be best predicted by artificial neural network method with an accuracy of about 80%.

Performance of ultra-small silicon photomultiplier array with active area of 0.12 mm×0.12 mm

Abstract We report the performance of an ultra-small silicon photomultiplier (SiPM) line array with 7 elements of 0.12×0.12 mm 2 in active area, 0.2 mm in pitch and 120 micro cells in one element. The device features an epitaxial bulk quenching resistor concept, demonstrated high geometrical fill factor of 41% and photon detection efficiency (PDE) of 25.4% in the wavelength region between 430 nm and 480 nm while retaining high micro cell density around 10 000 mm −2 and ~3 ns FWHM of dark pulses width; it also demonstrated dark count rate of less than 28.7 kHz, optical crosstalk of the order of 2% to 4%, and excellent photon number discrimination. A 0.15 mm×1.6 mm×1.6 mm lutetium yttrium oxyorthosilicate (LYSO) crystal, corresponding to the width, length and height respectively, was successfully coupled to the 1×7 SiPM array for possible ultra-highly resolved positron emission tomography (PET) applications. This novel type of device has advantages particularly for small active area since the performances, such as PDE and response speed is one of the best among SiPMs with similarly high density of micro cells. It may pave a way for this type of SiPM as a promising pixel position sensitive device in imaging sensor applications.

Correction: Corrigendum: Nanocrystalline ZnON; High mobility and low band gap semiconductor material for high performance switch transistor and image sensor application

Correction: Corrigendum: Nanocrystalline ZnON; High mobility and low band gap semiconductor material for high performance switch transistor and image sensor application

A 64 fJ/step 9-bit SAR ADC Array With Forward Error Correction and Mixed-Signal CDS for CMOS Image Sensors

A 9 b Successive-Approximation-Register (SAR) Anglog-to-Digital Converter (ADC) with pilot-Digital-to-Analog Converter (pDAC) technique for image sensor applications is described in this paper. Its Forward Error Correction (FEC) improves its robustness against device mismatch. It performs mixed-signal Correlated-Double-Sampling (CDS) using only the ADC's built-in capacitor array without any additional amplifier or memory. The ADC measures 490μm×7.4μm and is demonstrated in a low-power CMOS image sensors with column parallel ADCs. Measurement results from the prototype image sensor in 0.18 μm technology shows that the ADC's Differential Non-Linearity (DNL) is reduced from 3.5 LSB to 1.2 LSB by its mixed-signal FEC algorithm, making its Figure-of-Merit (FoM) 64 fJ/step. Furthermore, when combined with the ADC's mixed-signal Correlated-Double-Sampling, the column FPN is reduced from 3.2% to 0.5% without any additional circuit.

Architecture and applications of a high resolution gated SPAD image sensor.

We present the architecture and three applications of the largest resolution image sensor based on single-photon avalanche diodes (SPADs) published to date. The sensor, fabricated in a high-voltage CMOS process, has a resolution of 512 × 128 pixels and a pitch of 24 μm. The fill-factor of 5% can be increased to 30% with the use of microlenses. For precise control of the exposure and for time-resolved imaging, we use fast global gating signals to define exposure windows as small as 4 ns. The uniformity of the gate edges location is ∼140 ps (FWHM) over the whole array, while in-pixel digital counting enables frame rates as high as 156 kfps. Currently, our camera is used as a highly sensitive sensor with high temporal resolution, for applications ranging from fluorescence lifetime measurements to fluorescence correlation spectroscopy and generation of true random numbers.

Nanocrystalline ZnON; high mobility and low band gap semiconductor material for high performance switch transistor and image sensor application.

Interest in oxide semiconductors stems from benefits, primarily their ease of process, relatively high mobility (0.3–10 cm2/vs), and wide-bandgap. However, for practical future electronic devices, the channel mobility should be further increased over 50 cm2/vs and wide-bandgap is not suitable for photo/image sensor applications. The incorporation of nitrogen into ZnO semiconductor can be tailored to increase channel mobility, enhance the optical absorption for whole visible light and form uniform micro-structure, satisfying the desirable attributes essential for high performance transistor and visible light photo-sensors on large area platform. Here, we present electronic, optical and microstructural properties of ZnON, a composite of Zn3N2 and ZnO. Well-optimized ZnON material presents high mobility exceeding 100 cm2V−1s−1, the band-gap of 1.3 eV and nanocrystalline structure with multiphase. We found that mobility, microstructure, electronic structure, band-gap and trap properties of ZnON are varied with nitrogen concentration in ZnO. Accordingly, the performance of ZnON-based device can be adjustable to meet the requisite of both switch device and image-sensor potentials. These results demonstrate how device and material attributes of ZnON can be optimized for new device strategies in display technology and we expect the ZnON will be applicable to a wide range of imaging/display devices.

Vapor transport deposition of large‐area polycrystalline CdTe for radiation image sensor application

AbstractVapor transport deposition (VTD) process delivers saturated vapor to substrate, resulting in high‐throughput and scalable process. In addition, VTD can maintain lower substrate temperature than close‐spaced sublimation (CSS). The motivation of this work is to adopt several advantages of VTD for radiation image sensor application. Polycrystalline CdTe films were obtained on 300 mm×300 mm indium tin oxide (ITO) coated glass. The polycrystalline CdTe film has columnar structure with average grain size of 3 µm ∼ 9 µm, which can be controlled by changing the substrate temperature. In order to analyze electrical and X‐ray characteristics, ITO‐CdTe‐Al sandwich structured device was fabricated. Effective resistivity of the polycrystalline CdTe film was ∼1.4×109Ωcm. The device was operated under hole‐collection mode. The responsivity and the µτ product estimated to be 6.8 µC/cm2R and 5.5×10–7 cm2/V. The VTD can be a process of choice for monolithic integration of CdTe thick film for radiation image sensor and CMOS/TFT circuitry. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Multi-view space object recognition and pose estimation based on kernel regression

Abstract The application of high-performance imaging sensors in space-based space surveillance systems makes it possible to recognize space objects and estimate their poses using vision-based methods. In this paper, we proposed a kernel regression-based method for joint multi-view space object recognition and pose estimation. We built a new simulated satellite image dataset named BUAA-SID 1.5 to test our method using different image representations. We evaluated our method for recognition-only tasks, pose estimation-only tasks, and joint recognition and pose estimation tasks. Experimental results show that our method outperforms the state-of-the-arts in space object recognition, and can recognize space objects and estimate their poses effectively and robustly against noise and lighting conditions.

光り輝く日本のイメージセンサ技術とその応用の今後の取組み

光り輝く日本のイメージセンサ技術とその応用の今後の取組み

Two-Step Single Slope/SAR ADC with Error Correction for CMOS Image Sensor

Conventional two-step ADC for CMOS image sensor requires full resolution noise performance in the first stage single slope ADC, leading to high power consumption and large chip area. This paper presents an 11-bit two-step single slope/successive approximation register (SAR) ADC scheme for CMOS image sensor applications. The first stage single slope ADC generates a 3-bit data and 1 redundant bit. The redundant bit is combined with the following 8-bit SAR ADC output code using a proposed error correction algorithm. Instead of requiring full resolution noise performance, the first stage single slope circuit of the proposed ADC can tolerate up to 3.125% quantization noise. With the proposed error correction mechanism, the power consumption and chip area of the single slope ADC are significantly reduced. The prototype ADC is fabricated using 0.18 μm CMOS technology. The chip area of the proposed ADC is 7 μm × 500 μm. The measurement results show that the energy efficiency figure-of-merit (FOM) of the proposed ADC core is only 125 pJ/sample under 1.4 V power supply and the chip area efficiency is 84 k μm2 ·cycles/sample.

Surface Plasmon Resonance Image Sensor Module of Spin-Coated Silver Film with Polymer Layer

Prism modules of 20 nm-, 40 nm-, and 60 nm-thick spin-coated silver films both without and with an upper 100 nm-thick spin-coated polymer layer were fabricated for surface plasmon resonance (SPR) image sensor applications. The prism modules were applied to an SPR image sensor system. The coefficients of determination (R2s) for the 20 nm-, 40 nm- and 60 nm-thick silver films without the polymer layer were 0.9231, 0.9901, and 0.9889, respectively, and with the polymer layer 0.9228, 0.9951, and 0.9880, respectively when standard ethanol solutions with 0.1% intervals in the range of 20.0% to 20.5% were applied. The upper polymer layer has no effect on the R2. The prism modules of the 40-nm-thick spin-coated silver films had the highest R2 value of approximately 0.99. The durability of the 40 nm-thick spin-coated silver film with the 100 nm-thick polymer layer is much better than that without the upper low-loss polymer layer. The developed SPR image sensor module of the 40 nm-thick spin-coated silver film with the upper 100 nm-thick low-loss polymer film is expected to be a very cost-effective and robust solution because the films are formed at low temperatures in a short period of time without requiring a vacuum system and are very durable.

A low power discrete operation mode for punchthrough phototransistor

This paper proposed a discrete operation mode for a punchthrough (PT) phototransistor, which is suitable for low power application, since the bias current is only necessary during the read-out phase. Moreover, simulation results show that with the new operation mode, the photocurrent is much larger than that of continuous operation mode. An ultra-high responsivity of 2 × 107A/W at 10−9 W/cm2 is obtained with a small detector size of 1 μm2. In CMOS image sensor applications, with an integration time of 10 ms, a normalized pixel responsivity of 220 V·m2/W·s·μm2 is obtained without any auxiliary amplifier.

The Application of CMOS Image Sensor and ZigBee in Building Smart Home Solutions

The Application of CMOS Image Sensor and ZigBee in Building Smart Home Solutions

Photo-Related Stress Effects in a-SiGe:H Thin Film Transistors for Infrared Image Sensors

The effects of photo-related stress on the electrical performances of a-SiGe:H thin-film transistors (TFTs) were investigated in comparison with a-Si:H TFTs. Compared with a-Si:H TFTs, the a-SiGe:H TFTs show better stability to the light stress because the number of electrons involved in the creation of dangling bonds are smaller in a-SiGe:H TFTs, resulting in less light-induced degradation. However, a larger threshold voltage shift from the positive gate bias was observed due to the higher number of weak bonds in a-SiGe:H TFTs, which leads to a higher gate bias instability than is observed for a-Si:H TFTs. The temperature dependences of the electrical properties in a-SiGe:H TFTs were observed, and they indicated that a-SiGe:H TFTs follow a thermally activated behavior pattern. Based on the thermally activated behavior, a new model predicting the lifetime of a-SiGe:H TFT image sensors was proposed. The instability of the drain current with respect to the stress time under an electrical bias and light was estimated. Based on the calculated lifetime, the a-SiGe:H TFTs are predicted to be reliable for long-term applications in image sensors.

High-performance modulation-doped AlGaAs/InGaAs thermopiles for uncooled infrared FPA application

Abstract Novel thermopile based on modulation doped AlGaAs/InGaAs heterostructures is proposed and developed for the first time, for uncooled infrared FPA (Focal Plane Array) image sensor application. The high responsivity with the high speed response time are designed to be 4900 V/W with 110 μs under the 2 μm design rule. Based on integrated HEMT–MEMS technology, the 32 × 32 matrix FPA is fabricated to demonstrate its enhanced performances by black body measurement. The technology presented here demonstrates the potential of this approach for low-cost uncooled infrared FPA image sensor application.