2D Image Sensing Arrays with NIP Diodes

Berkel, C. van; Bird, N.C.; Curling, C. J.; French, I. D.

doi:10.1557/proc-297-939

Cited by 21 publications

(7 citation statements)

References 7 publications

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“…In the majority of these imaging devices, the pixel switch is a single thin-film transistor ͑TFT͒ made from amorphous silicon ͑a-Si:H͒ 1-6 although alternative approaches employing a cadmium selenide TFT, 7 a single a-Si:H diode, [8][9][10] or dual a-Si:H diodes 11 have also been reported. AMFPIs may further be divided into two categories depending upon whether the incident radiation is detected directly or indirectly.…”

Section: Introductionmentioning

confidence: 99%

Empirical investigation of the signal performance of a high‐resolution, indirect detection, active matrix flat‐panel imager (AMFPI) for fluoroscopic and radiographic operation

et al. 1997

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Signal properties of the first large-area, high resolution, active matrix, flat-panel imager are reported. The imager is based on an array of 1536 x 1920 pixels with a pixel-to-pixel pitch of 127 microns. Each pixel consists of a discrete amorphous silicon n-i-p photodiode coupled to an amorphous silicon thin-film transistor. The imager detects incident x rays indirectly by means of an intensifying screen placed over the array. External acquisition electronics send control signals to the array and process analog imaging signals from the pixels. Considerations for operation of the imager in both fluoroscopic and radiographic modes are detailed and empirical signal performance data are presented with an emphasis on exploring similarities and differences between the two modes. Measurements which characterize the performance of the imager were performed as a function of operational parameters in the absence or presence of illumination from a light-emitting diode or x rays. These measurements include characterization of the drift and magnitude of the pixel dark signal, the size of the pixel switching transient, the temporal behavior of pixel sampling and the implied maximum frame rate, the dependence of relative pixel efficiency and pixel response on photodiode reverse bias voltage and operational mode, the degree of linearity of pixel response, and the trapping and release of charge from metastable states in the photodiodes. In addition, X-ray sensitivity as a function of energy for a variety of phosphor screens for both fluoroscopic and radiographic operation is reported. Example images of a line-pair pattern and an anthropomorphic phantom in each mode are presented along with a radiographic image of a human hand. General and specific improvements in imager design are described and anticipated developments are discussed. This represents the first systematic investigation of the operation and properties in both radiographic and fluoroscopic modes of an imager incorporating such an array.

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Section: Introductionmentioning

confidence: 99%

Empirical investigation of the signal performance of a high‐resolution, indirect detection, active matrix flat‐panel imager (AMFPI) for fluoroscopic and radiographic operation

et al. 1997

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“…At biases higher than 0.75 V, where the current-voltage dependence is nonexponential, the forward current is space charge limited. 9 The reverse bias leakage current is one of the most important characteristics of the photodiode array since it determines the lowest detectable light level. For the fabricated photodiodes, the reverse dark current density is around 0.5 nA/cm 2 at Ϫ5 V bias, which is a little higher than the junction leakage reported for a-Si:H p-i-n photodiode arrays with continuous intrinsic layers.…”

Section: Photodiode Array Design and Fabricationmentioning

confidence: 99%

“…There are few reports on the successful implementation of the switching diodes for signal readout in flat-panel x-ray detectors and image sensors. [7][8][9] Switching diodes and photodiodes can be manufactured simultaneously using the same n-i-p layers, and the number of masks required in lithography can be reduced to 6 -7. The disadvantage of switching diodes lies in a less efficient charge transfer rate and a higher capacitance, which can lead to cross talk.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional a-Si:H based n-i-p sensor array

Chang

Vygranenko

Nathan

2004

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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This article presents the design and fabrication process of a two-dimensional hydrogenated amorphous silicon (a-Si:H) n-i-p photodiode array, developed for low light level sensor applications. Utilization of the single a-Si:H switching diode for signal readout enables simpler device design and fabrication. Since the sensing and switching diodes are formed simultaneously by dry etching the a-Si:H layers deposited over the whole area, the number of masks required in lithography was reduced to six. A significant reduction of the leakage current has been achieved by tailoring defects at the i-p interface and optimizing the plasma processing conditions. Details of device fabrication along with results of the sensor array performance are presented.

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“…Other possible applications may be found in the field of biotechnology, in particular in genomic analysis for the massively-parallel DNA detection. The single-switching diode readout technique is used to simplify device design and fabrication [3][4][5]. Recently, Fixe et al have reported on the use of an a-Si:H photodetector to measure the density of fluorescently-tagged biomolecules [2].…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional a-Si:H/a-SiC:H n-i-p sensor array with ITO/a-SiNx antireflection coating

2005

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This paper presents a two-dimensional a-Si:H/a-SiC:H n-i-p photodiode array with switching diode readout, developed specifically for fluorescence-based bio-assays. Both device structure and fabrication processing has enabled enhancement of the external quantum efficiency of the encapsulated device up to 80%, reduction of the photodiode leakage down to 10 pA/cm 2 at -1V reverse bias, and increase of the rectification current ratio of the switching diodes up to 10 9 . The critical fabrication issues associated with deposition of device-quality materials, tailoring of defects at the i-p interface, device patterning with dry etching, junction passivation, and contact formation will be discussed. Both sensing and switching diodes were characterized. While the observed dark current in the photodiodes at low reverse bias voltages is primarily due to carrier emission from deep states in the a-Si:H bulk, the leakage in the small switching diodes stems from peripheral defects along junction sidewalls. Optical losses in the photodiodes with ITO/a-SiN x :H antireflection coating were evaluated using numerical modeling, and the calculated transmission spectra correlated well with the spectral response characteristics. Measurements of the charge transfer time and output linearity demonstrated the efficiency of the single-switching diode readout configuration. The response of the array to optical excitation was also investigated. The observed long term retardation in the signal rise and decay at illumination levels less than 10 10 photons/cm 2 -s can be associated with charge trapping in the undoped layer.

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2D Image Sensing Arrays with NIP Diodes

Cited by 21 publications

References 7 publications

Empirical investigation of the signal performance of a high‐resolution, indirect detection, active matrix flat‐panel imager (AMFPI) for fluoroscopic and radiographic operation

Empirical investigation of the signal performance of a high‐resolution, indirect detection, active matrix flat‐panel imager (AMFPI) for fluoroscopic and radiographic operation

Two-dimensional a-Si:H based n-i-p sensor array

Two-dimensional a-Si:H/a-SiC:H n-i-p sensor array with ITO/a-SiNx antireflection coating

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