Transient Current Behavior of Vertically Integrated Amorphous Silicon Diodes

2007 ◽  
Vol 989 ◽  
Author(s):  
Gregory Choong ◽  
Nicolas Wyrsch ◽  
Christophe Ballif ◽  
Rolf Kaufmann ◽  
Felix Lustenberger
Keyword(s):  
Bias Voltage ◽  
High Sensitivity ◽  
Transient Behavior ◽  
Image Sensor ◽  
Image Sensors ◽  
Commercial Development ◽  
Active Pixel ◽  
Constant Bias ◽  
Pixel Sensors ◽  
A Charge

AbstractMonolithic image sensors based on Thin Film on CMOS (TFC) Technology are becoming more and more attractive as an alternative solution to conventional active pixel sensors (APS). Imager with high sensitivity, high dynamic coupled with low dark current values (10-100 pA/cm2 @ 104 V/cm) have been developed. However, issues such as light-induced degradation and image lag hinder the commercial development of a-Si:H based image sensors. The problem of image lag is caused by residual current due to the release of trapped charges after the switch off of the illumination.In this paper, we present a comprehensive study of the transient behavior of the photocurrent in a-Si:H photodiodes deposited on glass, as well as in corresponding diodes implemented in a TFC image sensor when illumination is switched off or periodically varied. The influence of the pixel architecture for two different cases is also analyzed: One setup reproduces the typical 3 transisor APS pixel architecture behavior, in which the bias voltage of the diode varies with the photogenerated charge while the second setup keeps a constant bias voltage applied to the diode by using a charge integrator.The influence of the light-induced defect creation on the performance of the sensors is also presented and discussed.

A 800(H) x 600(V) high sensitivity and high full well capacity CMOS image sensor with active pixel readout feedback operation

2008 ◽  
Author(s):  
Woonghee Lee ◽  
Nana Akahane ◽  
Satoru Adachi ◽  
Koichi Mizobuchi ◽  
Shigetoshi Sugawa
Keyword(s):  
High Sensitivity ◽  
Cmos Image Sensor ◽  
Image Sensor ◽  
Active Pixel

Performance of Photo-Transistors with thin (50 nm.) a-Si:H Layers

1995 ◽  
Vol 377 ◽  
Author(s):  
Serag M. GadelRab ◽  
Savvas G. Chamberlain
Keyword(s):  
Contact Resistance ◽  
High Sensitivity ◽  
Transient Behavior ◽  
Image Sensors ◽  
Optical Path ◽  
Transistor Structure ◽  
Optical Sensitivity

ABSTRACTPhoto-transistor based a-Si:H image sensors allow the integration of photo-elements and pixel circuitry using standard TFT fabrication processes. While pixel circuitry use thin a-Si:H films (≈ 0.05μm) to minimize the contact resistance, photo-transistors require thick a-Si:H films (≈0.5μm) to maximize photo-sensitivity. We fabricated a new, high sensitivity photo-transistor structure using 0.05μ a-Si:H films. High optical sensitivity is achieved by separating the conduction paths of photo-generated electrons and holes using a secondary gate. Further, the optical path within the photo-transistor is doubled through manipulation of device layout. The photo-transistor show an Ilight/Idarkratio in excess of 103.We compared the transient behavior of conventional and high-sensitivity photo-transistors. We found that both devices display an increase in current with time when biased in either the dark or illuminated conditions. The current increases by six orders of magnitudes then saturates within 200 seconds of bias application. Experiments indicate that this transient behavior is due to a rise in the conductivity of the gap region with time; measurements on 0.05μm thick photo-resistor structures showed that their current increases with time. The shape and temporal range of this behavior rules out the presence of parasitic capacitive effects.

scholarly journals A CMOS voltage-mode image sensing system

2021 ◽  
Author(s):  
Jun Long Zhang
Keyword(s):  
Cmos Image Sensor ◽  
Cmos Technology ◽  
Image Sensor ◽  
Electrical Signal ◽  
Image Sensors ◽  
Analog To Digital ◽  
Light Sensing ◽  
Image Sensing ◽  
Cmos Image Sensors ◽  
Pixel Sensors

A CMOS image sensor consists of a light sensing region that converts photonic energy to an electrical signal and a peripheral circuitry that performs signal conditioning and post-processing. This project investgates the principle and design of CMOS active image sensors. The basic concepts and principle of CMOS image sensors are investigated. The advantages of CMOS image sensors over charge-coupled device (CCD) image sensors are presented. Both passive pixel sensors (PPS) and acive pixel sensors (APS) are examined in detail. The noise of CMOS image sensors is investigated and correlated double sampling (CDS) techniques are examined. The design of APS arrays, CDS circuits and 8-bit analog to-digital converters in TSMC-0.18μm 1.8V CMOS technology is presented. The simulation results and layout of the designed CMOS image sensor are presented.

The Hybrid Pixel Sensors and Read-Out Electronics

2006 ◽  
Vol 113 ◽  
pp. 453-458 ◽  
Author(s):  
R. Navickas ◽  
V. Barzdenas
Keyword(s):  
Dynamic Range ◽  
High Sensitivity ◽  
Low Noise ◽  
Wide Dynamic Range ◽  
Pixel Detectors ◽  
Linear Behavior ◽  
Pixel Sensors ◽  
A Charge ◽  
Silicon Cmos ◽  
Physical Principles

Hybrid pixel sensors (detectors) have shown to be a valid alternative to other types of Xray imaging devices due to their high sensitivity, linear behavior and wide dynamic range, and low noise. One important feature of these devices is the fact that detectors and readout electronics are manufactured separately. The charge created by the interaction of X-ray photons in the sensor is very small and has to be amplified in a low-noise circuit before any further signal processing. The signal induced on the electrodes of the sensor is transferred to the readout chip, where it is integrated in a charge sensitive amplifier. The issue reviews on physical principles of operation and design of the hybrid pixel sensors developed on the basis of the silicon CMOS and GaAs MESFETtechnologies. The authors have designed GaAs charge sensitive amplifiers for hybrid pixel detectors and show the results of a simulation.

scholarly journals Interfacial electrostatic interaction-enhanced photomultiplication for ultra-high external quantum efficiency of organic photodiodes

2021 ◽  
Author(s):  
Juhee Kim ◽  
Mingyun Kang ◽  
Sangjun Lee ◽  
Chan So ◽  
Dae Sung Chung
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Electrostatic Interactions ◽  
High Sensitivity ◽  
Image Sensor ◽  
Image Sensors ◽  
Charge Carriers ◽  
Gain Bandwidth ◽  
Electron States ◽  
Trapped Electron

Abstract A photomultiplication-type organic photodiode (PM-OPD), where an electric double layer (EDL) is strategically embedded, is demonstrated with an exceptionally high external quantum efficiency (EQE) of 2,210,000%, responsivity of 11,200 A W− 1, specific detectivity of 2.82 × 1014 Jones, and gain-bandwidth product of 1.92 × 107 Hz as well as high reproducibility. A metal-semiconductor Schottky interface consisting of an EDL enables the stabilization of trapped electron states within the acceptor domains of the photoactive layer by electrostatic interactions, boosting the PM-OPD gain generation. The effects of the EDL on the energetics of trapped electron states are confirmed by numerical simulations based on the drift-diffusion approximation of charge carriers. The feasibility of the fabricated high-EQE PM-OPD is demonstrated via a pixelated prototype image sensor. We believe that this new OPD platform opens up the possibility for the ultra-high-sensitivity organic image sensors, while maintaining the advantageous properties of organics.

scholarly journals A CMOS voltage-mode image sensing system

2021 ◽  
Author(s):  
Jun Long Zhang
Keyword(s):  
Cmos Image Sensor ◽  
Cmos Technology ◽  
Image Sensor ◽  
Electrical Signal ◽  
Image Sensors ◽  
Analog To Digital ◽  
Light Sensing ◽  
Image Sensing ◽  
Cmos Image Sensors ◽  
Pixel Sensors

A CMOS image sensor consists of a light sensing region that converts photonic energy to an electrical signal and a peripheral circuitry that performs signal conditioning and post-processing. This project investgates the principle and design of CMOS active image sensors. The basic concepts and principle of CMOS image sensors are investigated. The advantages of CMOS image sensors over charge-coupled device (CCD) image sensors are presented. Both passive pixel sensors (PPS) and acive pixel sensors (APS) are examined in detail. The noise of CMOS image sensors is investigated and correlated double sampling (CDS) techniques are examined. The design of APS arrays, CDS circuits and 8-bit analog to-digital converters in TSMC-0.18μm 1.8V CMOS technology is presented. The simulation results and layout of the designed CMOS image sensor are presented.

scholarly journals Characterization and Optimization of a Single-Transistor Active Pixel Image Sensor with Floating Junction Connected to Floating Gate

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Xin-Yan Liu ◽  
Jun Wu ◽  
Xiao-Yong Liu ◽  
Shuai Zhang ◽  
Xi Lin ◽  
...  
Keyword(s):  
Transient Behavior ◽  
Optimization Methods ◽  
Image Sensor ◽  
Floating Gate ◽  
Transient Time ◽  
Light Sensing ◽  
Mechanism Optimization ◽  
Active Pixel ◽  
Pixel Image ◽  
Device Operation

The application of semifloating gate transistor (SFGT) as the single-transistor active pixel image sensor (APS) is investigated in this paper. This single-transistor (1T) APS can realize the functions of the conventional 3T CMOS image sensor. The device operation mechanism, optimization methods, and transient behavior measurements will be discussed. Because the floating junction of this device is connected to the floating gate, special behaviors such as floating gate voltage pinning effects were observed. The transient time measurement emulating the exposure procedure also confirmed the light sensing function as a single-transistor image sensor.

scholarly journals Front-Inner Lens for High Sensitivity of CMOS Image Sensors

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1536 ◽  
Author(s):  
Godeun Seok ◽  
Yunkyung Kim
Keyword(s):  
High Resolution ◽  
Aspect Ratio ◽  
High Sensitivity ◽  
Image Sensor ◽  
Image Sensors ◽  
Optical Simulation ◽  
Optical Performance ◽  
Pixel Size ◽  
Cmos Image Sensors ◽  
Pixel Pitch

Due to the continuing improvements in camera technology, a high-resolution CMOS image sensor is required. However, a high-resolution camera requires that the pixel pitch is smaller than 1.0 μm in the limited sensor area. Accordingly, the optical performance of the pixel deteriorates with the aspect ratio. If the pixel depth is shallow, the aspect ratio is enhanced. Also, optical performance can improve if the sensitivity in the long wavelengths is guaranteed. In this current work, we propose a front-inner lens structure that enhances the sensitivity to the small pixel size and the shallow pixel depth. The front-inner lens was located on the front side of the backside illuminated pixel for enhancement of the absorption. The proposed structures in the 1.0 μm pixel pitch were investigated with 3D optical simulation. The pixel depths were 3.0, 2.0, and 1.0 μm. The materials of the front-inner lens were varied, including air and magnesium fluoride (MgF2). For analysis of the sensitivity enhancement, we compared the typical pixel with the suggested pixel and confirmed that the absorption rate of the suggested pixel was improved by a maximum of 7.27%, 10.47%, and 29.28% for 3.0, 2.0, and 1.0 μm pixel depths, respectively.

scholarly journals 1/f Noise Modelling and Characterization for CMOS Quanta Image Sensors

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5459
Author(s):  
Wei Deng ◽  
Eric R. Fossum
Keyword(s):  
Analog Circuits ◽  
Image Sensor ◽  
Image Sensors ◽  
Correlated Double Sampling ◽  
Cmos Image Sensors ◽  
Source Follower ◽  
Cmos Analog Circuits ◽  
Different Origins ◽  
Noise Models ◽  
Fitting Model

This work fits the measured in-pixel source-follower noise in a CMOS Quanta Image Sensor (QIS) prototype chip using physics-based 1/f noise models, rather than the widely-used fitting model for analog designers. This paper discusses the different origins of 1/f noise in QIS devices and includes correlated double sampling (CDS). The modelling results based on the Hooge mobility fluctuation, which uses one adjustable parameter, match the experimental measurements, including the variation in noise from room temperature to –70 °C. This work provides useful information for the implementation of QIS in scientific applications and suggests that even lower read noise is attainable by further cooling and may be applicable to other CMOS analog circuits and CMOS image sensors.

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