Peripheral photoresponse of a p–n junction

A quantitative theory is presented for the enhanced photoresponse of p–n junctions that arises from the lateral diffusion of photogenerated carriers. This mechanism leads to a photoactive area for a photodiode that may be much larger than its p–n junction area. The main theory pertains to the geometry that arises with mesa diodes, the results for which are also applicable to planar junctions that are shallow when compared with the minority‐carrier diffusion length. The solution for infinitely deep planar junctions is obtained by separate analysis. The magnitude of the peripheral photoresponse is sensitive to geometric and physical factors such as semiconductor thickness, surface recombination, optical absorption length, and competition for photogenerated carriers by adjacent photodiodes. The dependence of the response upon all of these features is presented.