Photodetector comprising a pinned photodiode that is formed by an optically sensitive layer and a silicon diode
In various embodiments, a photodetector includes a semiconductor substrate and a plurality of pixel regions. Each of the plurality of pixel regions comprises an optically sensitive layer over the semiconductor substrate. A pixel circuit is formed for each of the plurality of pixel regions. Each pixel circuit includes a pinned photodiode, a charge store, and a read out circuit for each of the plurality pixel regions. The optically sensitive layer is in electrical communication with a portion of a silicon diode to form the pinned photodiode. A potential difference between two electrodes in communication with the optically sensitive layer associated with a pixel region exhibits a time-dependent bias; a biasing during a first film reset period being different from a biasing during a second integration period.
1. A photodetector comprising:
a semiconductor substrate;
a plurality of pixel regions, each of the plurality of pixel regions comprising an optically sensitive layer over the semiconductor substrate; and
a pixel circuit for each of the plurality of pixel regions, each pixel circuit comprising a pinned photodiode, a charge store, and a read out circuit for each of the plurality pixel regions, the optically sensitive layer being in electrical communication with a portion of a silicon diode to form the pinned photodiode, a potential difference between two electrodes in communication with the optically sensitive layer associated with a pixel region exhibits a time-dependent bias, a biasing during a first film reset period being different from a biasing during a second integration period;
the photodetector being configured to,
during a first integration time of a first frame, a floating photodetector is to be biased at near 0 V such that a pixel electrode and a common electrode have the same bias voltage, during which period the photodetector will not generate substantial photocurrent, and a readout signal is mainly from dark current from the silicon diode dark current, and
during a second frame integration, the floating photodetector is to be biased to operate in a normal condition, providing photocurrent to the diode node as a current sink or current source, and
first frame signals and second frame signals are to be subtracted to produce a net signal whose value substantially excludes an effect of silicon dark current.
2. A photodetector comprising:
a semiconductor substrate;
a plurality of pixel regions, each of the plurality of pixel regions comprising an optically sensitive layer over the substrate;
a pixel circuit for each of the plurality of pixel regions, each pixel circuit comprising a pinned photodiode, a charge store, and a read out circuit for each pixel region, the optically sensitive layer being in electrical communication with a portion of a silicon diode to form the pinned photodiode; the photodetector, following experiencing annealing at 150° C. or greater for 1 minute or greater, achieves light detection with a signal-to-noise ratio greater than 1 upon illumination by less than or equal to 0.05 lux of visible-wavelength light;
the photodetector being configured to,
during a first integration time of a first frame, a floating photodetector is to be biased at near 0 V such that a pixel electrode and a common electrode have the same bias voltage, during which period the photodetector will not generate substantial photocurrent, and a readout signal is mainly from dark current from the silicon diode dark current, and
during a second frame integration, the floating photodetector is to be biased to operate in a normal condition, providing photocurrent to the diode node as a current sink or current source, and
first frame signals and second frame signals are to be subtracted to produce a net signal whose value substantially excludes an effect of silicon dark current.
3. The photodetector of claim 2 , wherein the pinned photodiode resides in a plane of a silicon CMOS integrated circuit, and wherein an additional electrode resides on top of the optically sensitive layer.
4. The photodetector of claim 2 , further comprising a spectrally-selective filter, the spectrally-selective filter being formed above the photodetector and configured to substantially remove those wavelengths of light that are shorter than 400 nm.