High-Sensitivity Image Sensors Overlaid With Thin-Film Gallium Oxide/Crystalline Selenium Heterojunction Photodiodes

Imura, Shigeyuki; Kikuchi, Kenji; Miyakawa, Kazunori; Ohtake, Hiroshi; Kubota, Minoru; Okino, Toru; Hirose, Yutaka; Kato, Yasuyuki; Teranishi, Nobukazu

doi:10.1109/ted.2015.2441774

Cited by 22 publications

(10 citation statements)

References 12 publications

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“…Based on previous studies, heat treatment could accelerate the transformation of amorphous selenium to crystalline selenium, and Imura et al . have successfully prepared polycrystalline films consisting of nanoparticles by in situ thermal treatment for photodetector applications . The preferable growth of 1D Se nanorods is kinetically favored, since the binding energy of Se atoms along the c -axis is much higher than that along the ⟨12̅10⟩ directions .…”

Section: Resultsmentioning

confidence: 99%

Controlled Growth of a Large-Size 2D Selenium Nanosheet and Its Electronic and Optoelectronic Applications

et al. 2017

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Selenium has attracted intensive attention as a promising material candidate for future optoelectronic applications. However, selenium has a strong tendency to grow into nanowire forms due to its anisotropic atomic structure, which has largely hindered the exploration of its potential applications. In this work, using a physical vapor deposition method, we have demonstrated the synthesis of large-size, high-quality 2D selenium nanosheets, and the minimum thickness of which could be as thin as 5 nm. The Se nanosheet exhibits a strong in-plane anisotropic property, which is determined by angle-resolved Raman spectroscopy. Back-gating field-effect transistors (FETs) based on Se nanosheet exhibit p-type transport behaviors with on-state current density around 20 mA/mm at Vds=3V. Four-terminal field-effect devices are also fabricated to evaluate the intrinsic hole mobility of selenium nanosheet, and the value is determined to be 0.26 cm 2 V -1 s -1 at 300 K. The selenium nanosheet phototransistors show an excellent photoresponsivity up to 263 A/W, with the rise time of 0.1s and fall time of 0.12s. These results suggest that crystal selenium as a 2D form of 1D van der Waals solid, opens more feasibility to explore device applications.

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Section: Resultsmentioning

confidence: 99%

Controlled Growth of a Large-Size 2D Selenium Nanosheet and Its Electronic and Optoelectronic Applications

et al. 2017

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“…Next, a crystallization transition displays the various diffraction peaks in XRD patterns after annealing at 62 °C, corresponding to the darker color shown in practicality photographs. The darker color property of the polycrystalline Se (p-Se) is due to the strong optical absorptions in the visible range of long wavelengths [13], which will also be evidenced in the transmittance analysis section. It can be seen that the crystallization temperature at 62 °C for a-Se thin films is higher than for those of a-Se thick films [11,12], which is attributed to the significant influence from substrate surface.…”

Section: Resultsmentioning

confidence: 99%

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

Zhu

Yang

et al. 2018

Materials

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Amorphous selenium (a-Se) thin films with a thickness of 1200 nm were successfully fabricated by thermal evaporation at a low vacuum degree of 10−2 Pa. The structural properties involving phase and morphology showed that a-Se thin films could be resistant to 60 °C in air. Also, a transformation to polycrystalline Selenium (p-Se) was shown as the annealing temperature rose to 62 °C and 65 °C, with obvious changes in color and surface morphology. Moreover, as the a-Se transformed to p-Se, the samples’ transmittance decreased significantly, and the band gap declined dramatically from 2.15 eV to 1.92 eV. Finally, the X-radiation response of a-Se was investigated as an important property, revealing there is a remarkable response speed of photogeneration current both X-ray on and X-ray off, with a requirement of only a very small electrical field.

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“…Avalanche multiplication was first observed in a c-Sebased film fabricated on a glass substrate at a relatively low applied voltage, which exhibits high external quantum efficiency of over 100% 19) . However, avalanche multiplication could not be observed on pixel circuits with a silicon substrate 20) . This paper is organized as follows.…”

Section: Introductionmentioning

confidence: 94%

“…A 300-nm-thick a-Se film was deposited in vacuum on the sensor chip, and it was annealed at 200 °C to convert a-Se to c-Se. A 20-nm-thick n-Ga 2O 3 film was then formed by RF magnetron sputtering, and a 30-nm-thick ITO film was deposited on it by DC magnetron sputtering 20) . Table 1 multiplication is thought to be avalanche multiplication.…”

Section: Mechanism Of Generation Of Large Spot Noisementioning

confidence: 99%

[Paper] Analysis of Using Holes as Carriers in the Film in an 8K Stacked CMOS Image Sensor Overlaid with a Crystalline-Selenium Multiplication Layer

Arai¹,

Imura²,

Watabe³

et al. 2020

MTA

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A prototyped 8K stacked CMOS image sensor overlaid with a crystalline-selenium-based avalanche-multiplication layer, in which holes are used as traveling carriers in the film, was fabricated. Analysis of energy-band diagrams through the film to the n-type floating-diffusion region revealed that (i) large spot noise in the captured image could be suppressed and (ii) the high voltage required for avalanche multiplication could be applied to the film by using holes as carriers even when defects existed in the film. According to the results of experiments, no large spot noise occurred when the voltage applied to the film was +5 V. Additionally, the photoelectric-conversion current was increased by 1.4 times compared to the saturation-signal level when the applied voltage was +21.6 V. These results confirm charge multiplication in a crystalline-selenium-based stacked CMOS image sensor.

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High-Sensitivity Image Sensors Overlaid With Thin-Film Gallium Oxide/Crystalline Selenium Heterojunction Photodiodes

Cited by 22 publications

References 12 publications

Controlled Growth of a Large-Size 2D Selenium Nanosheet and Its Electronic and Optoelectronic Applications

Controlled Growth of a Large-Size 2D Selenium Nanosheet and Its Electronic and Optoelectronic Applications

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

[Paper] Analysis of Using Holes as Carriers in the Film in an 8K Stacked CMOS Image Sensor Overlaid with a Crystalline-Selenium Multiplication Layer

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