Low light adaptive imaging device

A low light adaptive photoelectric imaging device comprising:

• a phototransistor having an intrinsic gate, an extrinsic gate, and a drain,
• wherein the intrinsic gate is formed in an intrinsic semiconductor material and the extrinsic gate is formed in an extrinsic semiconductor material,
• wherein the phototransistor is configured to receive incident light at least at the extrinsic gate and to convert the received incident light into an electric charge that varies responsive to an intensity of the received incident light,
• wherein the extrinsic gate and the drain are extrinsically doped such that a depletion capacitance between the intrinsic gate and the drain differs from a depletion capacitance between the intrinsic gate and the extrinsic gate effective to form an electric potential barrier in the phototransistor,
• the electric potential barrier effective to cause a gain of the phototransistor to non-linearly vary responsive to the intensity of the received incident light.

A method of manufacturing a low light adaptive photoelectric imaging device, the method comprising:

• forming an extrinsic well in a semiconductor substrate;
• forming an intrinsic region in the extrinsic well;
• forming a source by doping a first portion of the intrinsic region as a first polarity type of semiconductor material;
• forming a drain by doping a second portion of the intrinsic region as the first polarity type of semiconductor material;
• forming a light-sensitive gate by doping a third portion of the intrinsic region as a second polarity type of semiconductor material, at least a portion of the light-sensitive gate being located between the source and the drain;
• wherein the drain and light-sensitive gate of the phototransistor are doped to facilitate formation of a depletion capacitance between the intrinsic region and the drain that differs from a depletion capacitance between the intrinsic region and the light-sensitive gate such that an electric potential barrier is formed during operation of the imaging device,
• the electric potential barrier being effective to cause a gain of the photoelectric imaging device to non-linearly vary responsive to an incident light intensity.

The method of claim 30, the method further comprising:

• forming a first switch device coupled to the drain;
• and
• forming a second switch device coupled to the light sensitive gate,
• wherein forming the first switch device includes:
• forming a first extrinsic region by doping a fourth portion of the intrinsic region as the first polarity type of semiconductor material;
• and
• forming a first gate electrode coupled between the first extrinsic region and the drain, the first switch device being selectively activated when a switch-activating signal is applied to the first gate electrode, and
• wherein forming the second switch device includes:
• forming a second extrinsic region by doping a fifth portion of the intrinsic region as the second polarity type of semiconductor material;
• and
• forming a second gate electrode coupled between the second extrinsic region and the light-sensitive gate, the second switch being selectively activated when a switch-activating signal is applied to the second gate electrode.