Samsung Patents an Image Sensor with Asymmetric Sub-Pixel Doping Layers

By Patentlyze Team · Updated May 22, 2026

Samsung's latest patent describes an image sensor where neighboring sub-pixels deliberately use different doping concentrations — a subtle but potentially significant tweak to how light-to-signal conversion is tuned at the silicon level.

What Samsung's asymmetric sub-pixel sensor actually does

Imagine your phone's camera sensor as a grid of tiny light-collecting buckets. Each bucket captures photons and converts them into an electrical signal. To make that conversion efficient, chipmakers carefully "dope" the silicon — adding controlled impurities to steer how electrons flow inside the chip.

In Samsung's design, each color region contains two sub-regions (think: two adjacent mini-buckets) that share a single charge-collection node called a floating diffusion. The twist is that these two sub-regions are not identical — one has a higher doping concentration in a key layer than the other. That asymmetry gives engineers a way to tune how each sub-pixel responds to light independently, even though they're physically paired.

The practical goal is likely better control over dynamic range and noise performance — the qualities that determine how well your camera handles bright highlights and dark shadows in the same shot.

How the doped regions and shared FD node interact

The patent describes a CMOS image sensor built on a substrate that's divided into color unit regions by an outer separation structure (essentially insulating walls etched into the silicon). Each color unit region holds multiple sub-regions plus a floating diffusion (FD) region — the node where collected charge accumulates before being read out as a voltage signal.

Each sub-region has a layered doping stack:

• A first doped region (p-type or n-type) sits right at the surface of the substrate
• A second doped region of the opposite conductivity type sits deeper in the silicon — this is the photodiode's main charge-storage layer
• A third doped region, same conductivity type as the first, sits even deeper still

The key claim: the second doped region's concentration differs between the first and second sub-regions. Because that middle layer governs how much charge a photodiode can hold (its "full-well capacity") and how it saturates, making it asymmetric effectively gives the two sub-regions different sensitivity levels.

This is architecturally similar to dual-gain pixel designs used in HDR sensors, where pairing a high-sensitivity and a lower-sensitivity photodiode within one unit lets the sensor capture both shadows and highlights without blowing out.

What this means for mobile camera sensor design

For Samsung's sensor division — which supplies imaging chips to its own Galaxy phones and many third-party manufacturers — squeezing more dynamic range and noise control out of each pixel without enlarging pixel pitch is a constant engineering challenge. An asymmetric doping scheme embedded at the fabrication level could offer a more robust path to HDR imaging than software-side frame stacking, which adds latency and motion blur.

For consumers, better-tuned sub-pixel doping translates to cameras that handle tricky lighting — a bright window behind a subject, a sunset scene — with less clipping and more detail. Whether this specific architecture makes it into a shipping sensor is another question, but it signals Samsung is working on HDR at the foundational silicon layer, not just the ISP.

Editorial commentary on a publicly published patent application. Not legal advice.