The Effect of Pinned Photodiode Shape on Time-of-Flight Demodulation Contrast

Millar, Terrence Cole; Sarhangnejad, Navid; Katic, Nikola; Kutulakos, Kiriakos N.; Genov, Roman

doi:10.1109/ted.2017.2677201

Cited by 22 publications

(5 citation statements)

References 24 publications

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“…This leads to a large value of stray electrons lost due to being collected by the other detector terminal. The modulation contrast, MC, given by the following equation in [16], is a widely adopted benchmark to quantify the effectiveness of carrier collection, and it can be calculated using:…”

Section: Performance Limitation Of Traditional Gapdmentioning

confidence: 99%

A CMOS-Compatible Gate-Assisted Photonic Demodulator With Contrast Enhancement for Time-of-Flight Sensing

Xiong,

Dai,

Estrada

et al. 2023

IEEE J. Electron Devices Soc.

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This paper presents a CMOS-compatible gateassisted photonic demodulator with contrast enhancement (GAPD-CE) techniques. To form an asymmetric field inside the substrate that will facilitate the transfer of photogenerated electrons, p-well and channel doping techniques are applied under the polysilicon guides. Modulation contrast (MC) values extracted from TCAD simulation show that the modified structure effectively collects electrons generated deep within the substrate. A prototype of the GAPD-CE is fabricated in a 0.18-μm standard CMOS foundry process. An MC of 83% and 57% at 1 MHz and 30 MHz, respectively, are achieved under 850 nm illumination, demonstrating the potential of the proposed device for time-offlight (ToF) sensing applications.

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Section: Performance Limitation Of Traditional Gapdmentioning

confidence: 99%

A CMOS-Compatible Gate-Assisted Photonic Demodulator With Contrast Enhancement for Time-of-Flight Sensing

Xiong,

Dai,

Estrada

et al. 2023

IEEE J. Electron Devices Soc.

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“…The higher the demodulation contrast(DC), the higher speed of charge transfer, the better the pixel's ability to separate charge, and the higher the performance of the pixel. The method in [6] is used to estimate the DC. The potential difference V1 of FD1 and the potential difference V2 of FD2 are respectively used to replace the number of collected electrons of FD1 and FD2, so that DC can be estimated by the (4).…”

Section: B Performance Metricsmentioning

confidence: 99%

“…The other one is to optimize the potential profile of n-well in PPD. [3], [4], [6], [7] achieve this by adjusting the shape of the pixels. [8], [9] introduce the effect of the pinning potential of PPD.…”

Section: Introductionmentioning

confidence: 99%

“…[8], [9] introduce the effect of the pinning potential of PPD. [6], [10], [11] introduce the staircase doping profiles of n-well generated from step implantation, which can optimize the lateral electric field of n-well. Especially, by changing the angle of implantation and the thickness and position of the photoresist, [11] realizes the staircase doping profiles by only one mask.…”

Section: Introductionmentioning

confidence: 99%

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Analyses of Pinned Photodiodes With High Resistivity Epitaxial Layer for Indirect Time-of-Flight Applications

Fang

Yang

et al. 2020

IEEE Access

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This paper analyzes the performance of pinned photodiode (PPD) for Time-of-Flight(ToF) applications on high resistivity epitaxial wafers. Due to its wide depletion region, high epitaxial resistivity PPDs feature some key advantages in collecting photogenerated charges. This paper compares the demodulation contrast of the same pixel design on epitaxial wafers with different resistivity at near-infrared wavelength to analyze their performance. By comparing the simulated profile of pixels with different epitaxial resistivity, the characteristics of the PPD pixel on high resistivity epitaxial wafer when collecting photogenerated charges are concluded. This paper also discusses the effects of using high resistivity epitaxial wafer with various design parameters. It is found that the use of high resistivity epitaxial wafer can greatly improve crosstalk performance, allow pixels to work at higher modulation frequencies, and enable largesized pixels to have good demodulation capabilities. INDEX TERMSPinned photodiode, time-of-flight, ToF, high resistivity, CMOS image sensor.

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“…The PPD is usually associated with a transfer gate (TG), which transfers the electrons accumulated during illumination within the photodiode to the sense node (SN), having lower capacitance and hence providing a readable voltage variation. The PPD/TG interface is becoming more critical for further improvements [5] in advanced applications, e.g., subelectron read noise levels [6], [7], high frame rates [8], [9], and time of flight (ToF) [10], [11]. Moreover, the nonideal effects due to the charge transfer mechanism from the PPD to the SN, which affects both the static and dynamic operations, has recently become a new research topic [12]- [14].…”

Section: Introductionmentioning

confidence: 99%

Compact Modeling of Charge Transfer in Pinned Photodiodes for CMOS Image Sensors

Capoccia

Boukhayma

Jazaeri

et al. 2019

IEEE Trans. Electron Devices

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In this paper, we propose a physics-based compact model of the pinned photodiode (PPD) combined with the transfer gate. A set of analytical expressions is derived for the 2-D electrostatic profile, the PPD capacitance, and the charge transfer current. The proposed model relies on the thermionic emission current mechanism, the barrier modulation, and the full-depletion approximation to obtain the charge transfer current. The proposed physics-based model is fully validated with technology computer-aided design simulations, i.e., stationary and optoelectrical simulations. The development of such a compact model for PPD represents an essential step toward the design, simulation, and optimization of PPD-based pixels in CMOS image sensors. Index Terms-Charge transfer, CMOS image sensors (CISs), compact modeling, pinned photodiode (PPD).

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The Effect of Pinned Photodiode Shape on Time-of-Flight Demodulation Contrast

Cited by 22 publications

References 24 publications

A CMOS-Compatible Gate-Assisted Photonic Demodulator With Contrast Enhancement for Time-of-Flight Sensing

A CMOS-Compatible Gate-Assisted Photonic Demodulator With Contrast Enhancement for Time-of-Flight Sensing

Analyses of Pinned Photodiodes With High Resistivity Epitaxial Layer for Indirect Time-of-Flight Applications

Compact Modeling of Charge Transfer in Pinned Photodiodes for CMOS Image Sensors

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