A photodiode is a semiconductor device used as a light detector or sensor. There are three types of photodiodes: P-N, PIN, and Avalanche photodiodes.
P-N junction photodiode
The P-N junction photodiode is the most fundamental type, with a structure similar to that found in solar cells. It operates on the photovoltaic effect, generating an electric current and voltage when exposed to light. While its response time is relatively slow, its low dark current makes it suitable for precise light-intensity measurements.
PIN photodiode
PIN photodiode has a structure in which an intrinsic semiconductor (i-layer) is sandwiched between a P-type semiconductor and an N-type semiconductor. A reverse bias voltage is applied across the i-layer. It features a fast response time and low dark current.
Avalanche photodiode (APD)
Avalanche photodiode (APD) has a P-type semiconductor divided into three layers: a P+ layer, an i-layer (P+ layer), and a P layer, with an N+ layer touching the P layer next. It is characterized by the amplification function by avalanche phenomenon in the P and N+ layers. APD has a high-speed response and the ability to detect weak light with high sensitivity.
Phototransistors are similar to photodiodes. A phototransistor is a photodiode and a transistor integrated into a single unit. The resulting photocurrent is internally amplified by the transistor.
Photodiodes are particularly useful in analyzers, measuring instruments, and optical signal detection in optical communications.
- Related words:
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- Photodiode
- P-N junction
- PIN
- Avalanche photodiodes (APD)
- Photo-detector
- Photo-sensor
- Dark current
- Response time
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