fotodiodarr

Fotodiodarr, commonly referred to in English as photodiodes, are semiconductor devices that convert light into electrical current or voltage. They are typically operated in reverse bias to maximize speed and dynamic range, though zero-bias photovoltaic operation is used for simple light detection with low noise.

The basic structure is a p-n junction or PIN junction; variants include avalanche photodiodes (APD) with internal gain. Materials are chosen for spectral response: silicon covers visible to near infrared (~200–1100 nm), germanium and SiGe extend into the near infrared; InGaAs devices detect around 900–1700 nm, and GaN or SiC enable UV sensitivity.

Key parameters include responsivity, quantum efficiency, spectral response, dark current, noise, bandwidth, and junction capacitance. In reverse bias the depletion region widens, lowering capacitance and increasing speed, at the cost of higher dark current. APDs add gain but introduce excess noise.

Operating modes include photovoltaic (zero bias), photoconductive (reverse bias), and APD mode for gain. Device size and geometry trade off area, capacitance, and speed.

Applications span fiber-optic receivers, spectroscopy, medical instrumentation, environmental sensing, LIDAR, and imaging sensors. They are often paired with transimpedance amplifiers to convert current to voltage and optimize noise performance.