Solid-state image sensor and imaging device
AssigneePanasonic Intellectual Property Management Co., Ltd.
InventorsShigetaka Kasuga, Manabu Usuda, Kentaro Nakanishi
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Abstract
A solid-state image sensor includes a pixel array including pixel cells arranged in a matrix. Each of the pixel cells includes an avalanche photodiode, a floating diffusion which accumulates charges, a transfer transistor which connects a cathode of the avalanche photodiode to the floating diffusion, a first reset transistor for resetting charges collected in the cathode of the avalanche photodiode, a second reset transistor for resetting charges accumulated in the floating diffusion, an amplification transistor for converting a charge amount of charges accumulated in the floating diffusion into a voltage, a memory which accumulates charges, and a count transistor which connects the floating diffusion to the memory.
Claims13
A solid-state image sensor, comprising:
- a pixel array including pixel cells arranged in a matrix,
- wherein each of the pixel cells includes:
- an avalanche photodiode having a first mode in which a charge amount of charges approximately proportional to the number of photons which cause photoelectric conversion is collected in a cathode of the avalanche photodiode when photons enter the avalanche photodiode under application of a first bias, and a second mode in which a saturated amount of charges is collected in the cathode when photons enter the avalanche photodiode under application of a second bias having a larger potential difference from a potential difference of the first bias and one photon causes photoelectric conversion;
- a floating diffusion which accumulates charges;
- a transfer transistor which connects the cathode of the avalanche photodiode and the floating diffusion;
- a first reset transistor for resetting charges collected in the cathode of the avalanche photodiode;
- a second reset transistor for resetting charges accumulated in the floating diffusion;
- an amplification transistor for converting a charge amount of the charges accumulated in the floating diffusion into a voltage;
- a memory which accumulates charges;
- and
- a count transistor which connects the floating diffusion and the memory,
- wherein, in a case where the avalanche photodiode is in the second mode, a potential barrier between a source and a drain of the transfer transistor when the transfer transistor is turned on is higher than a potential level of the cathode of the avalanche photodiode, the transfer transistor being turned on for redistributing the charges accumulated in the cathode to the cathode and to the floating diffusion.
Dependencies are inferred from the claim text.