Photosensitive imaging devices and associated methods
A monolithic sensor for detecting infrared and visible light according to an example includes a semiconductor substrate and a semiconductor layer coupled to the semiconductor substrate. The semiconductor layer includes a device surface opposite the semiconductor substrate. A visible light photodiode is formed at the device surface. An infrared photodiode is also formed at the device surface and in proximity to the visible light photodiode. A textured region is coupled to the infrared photodiode and positioned to interact with electromagnetic radiation.
1. An imager device, comprising:
a plurality of rows of photodiodes for detecting impinging electromagnetic radiation and accumulating an electrical charge;
a global transfer gate transistor coupled to the photodiodes for gating the photodiodes, wherein an open state of the global transfer gate transistor causes the electrical charge from the photodiodes to accumulate at an accumulation node;
a transfer gate transistor coupled to the accumulation node for gating the accumulation node, wherein an open state of the transfer gate transistor causes the electrical charge from the accumulation node to accumulate as a signal at a floating diffusion node;
a source follower transistor coupled to the floating diffusion node and configured to receive the signal from the floating diffusion node, wherein the source follower transistor amplifies the signal;
a row select gate transistor coupled to the source follower transistor, wherein the row select gate transistor reads out the signal from successive of the plurality of rows of photodiodes;
a reset gate transistor coupled between a voltage source and the floating diffusion node, wherein an open state of the reset gate transistor resets the electrical charge at the floating diffusion node;
a global reset transistor coupled between the photodiodes and the voltage source, wherein an open state of the global reset transistor prevents accumulation of the electrical charge at the photodiodes; and
a clock coupled to the global reset transistor and synchronized with pulses of a pulsed light source to create the global reset transistor open state between the pulses.
2. The device of claim 1 , wherein at least one photodiode of the plurality of rows of photodiodes further includes:
a semiconductor material having a doped region forming a junction and a light diffusion region coupled to the semiconductor material, the light diffusion region being positioned to interact with electromagnetic radiation.
3. The device of claim 2 , wherein the light diffusing region is a textured region.