Photoelectric converter

A photoelectric converter comprising a multiplicity of photosensor elements disposed in a matrix of rows and columns in a semiconductor body, each photosensor element comprising:

• a transistor including
• a first semiconductor region having a first conductivity type, a first conductor, and an ohmic contact layer disposed between the first semiconductor region and the first conductor and comprising a semiconductor having the same conductivity type as and a higher impurity concentration than the first semiconductor region,
• a second semiconductor region disposed contiguous to the first semiconductor region, the second semiconductor region having the same conductivity type as and a lower impurity concentration than the first semiconductor region,
• a third semiconductor region disposed contiguous to the second semiconductor region and having a different conductivity type from that of the second semiconductor region, an electrically insulating region disposed contiguous to the third semiconductor region, and a second conductor connected to the electrically insulating region;
• said third semiconductor region, said electrically insulating region and said second conductor in combination being arranged to constitute a capacitor;
• and
• a fourth semiconductor region disposed contiguous to the third semiconductor region and having a different conductivity type from that of the third semiconductor region, and a third conductor;
• said multiplicity of photosensor elements being isolated from each other with respect to their essential parts by element isolation regions,
• whereby said third semiconductor region is in a floating state so that the third semiconductor region stores a charge generated by photoexcitation by controlling the potential of the third semiconductor region through said electrically insulating region, an electric signal corresponding to the charge stored in the third semiconductor region is read out from the third conductor, and then the stored charge is refreshed through the third conductor.

A photoelectric converter comprising a photosensor element which in turn comprises a first transistor and a second transistor,

• said first transistor including a first conductor, a first semiconductor region connected to the first conductor, a second semiconductor region, a high-resistivity third semiconductor region, and a fourth semiconductor region, and
• said second transistor including said said second semiconductor region, said high-resistivity third semiconductor region, said fourth semiconductor region, a fifth semiconductor region, and a second conductor connected to the fifth semiconductor region,
• said first semiconductor region and said fifth semiconductor region having conductivity types different from each other, said second semiconductor region having a different conductivity type from that of the first semiconductor region and being disposed contiguous to said first semiconductor region, said fourth semiconductor region having a different conductivity type from that of the fifth semiconductor region and being disposed contiguous to said fifth semiconductor region, said high resistivity third semiconductor region being disposed between said second and fourth semiconductor regions and electrically connecting said second and fourth semiconductor regions,
• one of said second and fourth semiconductor regions functioning to store holes of electron-hole pairs generated by photo-excitation and the other to store electrons.

A photoelectric converter comprising a multiplicity of photosensor elements disposed in a matrix of rows and columns in a semiconductor body, each photosensor element comprising:

• a first transistor including a first conductor, a first semiconductor region connected to the first conductor, a second semiconductor region, a high-resistivity third semiconductor region, and a fourth semiconductor region, and
• a second transistor including said second semiconductor region, said high resistivity third semiconductor region, said fourth semiconductor region, a fifth semiconductor region, and a second conductor connected to the fifth semiconductor region,
• said first semiconductor region and said fifth semiconductor region having a conductivity types different from each other, said second semiconductor region having a different conductivity type from that of the first semiconductor region and being disposed contiguous to said first semiconductor region, said fourth semiconductor region having a different conductivity type from that of the fifth semiconductor region and being disposed contiguous to said fifth semiconductor region, said high-resistivity third semiconductor region being disposed between said second and fourth semiconductor regions and electrically connecting said second and fourth semiconductor regions,
• one of said second and fourth semiconductor regions functioning to store holes of electron-hole pairs generated by photo-excitation and the other to store electrons.

A photoelectric converter comprising a photosensor element, said photosensor element comprising:

• a first transistor including
• a first and a second semiconductor region respectively having a first conductivity type, a first and a second conductor connected to the first and second semiconductor regions, respectively, and
• a third semiconductor region having a second conductivity type opposite to the first conductivity type and being in a floating state;
• a second transistor including
• a fourth semiconductor region having said second conductivity type and directly connected to said third semiconductor region,
• a fifth semiconductor region having said second conductivity type,
• a third conductor connected to the fifth semiconductor region, and
• a sixth semiconductor region having said first conductivity and being in a floating state;
• and
• a fourth conductor connected to said sixth semiconductor region through an electrically insulating layer so as to control the potential of the sixth semiconductor region.

A photoelectric conversion process comprising the steps of:

• (A) providing a photoelectric converter comprising:
• a transistor including
• a first semiconductor region having a first conductivity type, a first conductor, and an ohmic contact layer disposed between the first semiconductor region and the first conductor and comprising a semiconductor having the same conductivity type as and a higher impurity concentration than the first semiconductor region,
• a second semiconductor region disposed contiguous to the first semiconductor region, the second semiconductor region having the same conductivity type as and a lower impurity concentration than the first semiconductor region,
• a third semiconductor region disposed contiguous to the second semiconductor region and having a different conductivity type from that of the second semiconductor region, an electrically insulating region disposed contiguous to the third semiconductor region, and a second conductor connected to the electrically insulating region;
• said third semiconductor region, said electrically insulating region and said second conductor in combination being arranged to constitute a capacitor;
• and
• a fourth semiconductor region disposed contiguous to the third semiconductor region and having a different conductivity type from that of the third semiconductor region, and a third conductor;
• (B) sequentially and cyclically conducting the following stages of operations:
• (a) Charge Storage Operation, comprising
• setting the following initial conditions wherein:
• the first semiconductor region is held at a reverse polarity of voltage,
• the third semiconductor region is biased to a reverse polarity of voltage, and
• the fourth semiconductor region is grounded or floated and
• illuminating the photosensor element with incident light to store a charge corresponding to the incident light in the third semiconductor region,
• (b) Readout Operation, comprising
• holding the fourth semiconductor region in a floating state and forward biasing the third semiconductor region to output an electrical signal corresponding to the charge in the third semiconductor region;
• and
• (C) Refreshing Operation, comprising
• holding the first semiconductor region at a ground potential or a reverse polarity of voltage,
• holding the fourth semiconductor region at ground potential, and
• applying a forward polarity of voltage to the third semiconductor region to remove a charge remaining corresponding the photogenerated charge in the third semiconductor region.