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0.4 Applications: The Photodiode


Photodiode Package A photodiode is packaged into a small can with two leads and an optical window on top

Photodiode Illumination Inside the package is the actual photodiode chip, illuminated through the optical window with the incident light often focused by a lens

Internal Connections Wire bonds connect the external leads to the photodiode chip. One connection is made to the top of the chip and one to the back of the chip. The back contact also acts as ground and is connected to the case

Photodiode Chip The photodiode chip contains the actual photodiode with a characteristic round top contact ring attached to the bonding pad

Photon Absorption Incident photons enter the semiconductor and are gradually absorbed as they penetrate the semiconductor

Electron-hole Pair Generation Electron-hole pairs are formed as the photon is absorbed. These carriers then drift towards the region where they are majority carriers