Photodiodes

A photodiode is a semiconductor device that converts light into electrical signals and is a core component in optoelectronic devices. Its operating principle is based on the photoelectric effect: when photon energy exceeds the semiconductor’s bandgap, electron-hole pairs are excited, generating a photocurrent.

 

1. What are the Key Characteristics of Photodiodes?

Spectral Response Range: Covers the ultraviolet to infrared wavelengths (typically 190-1100nm).

 

Response Speed: High-speed devices (such as PIN diodes) can reach nanoseconds, while avalanche diodes can respond even faster.

 

Dark Current: A key parameter measuring device noise (nA for standard diodes, pA for low-noise diodes).

 

Quantum Efficiency: A key indicator of light-to-electricity conversion efficiency (reaching over 90%).

 

2. What are the Types of Photodiodes?

Type

Structural Features

Typical Applications

PN Junction

Basic structure, low cost

Light intensity detection, simple optical communication

PIN

Intrinsic layer improves response speed

High-speed optical communication

Avalanche diode (APD)

 Internal gain mechanism

Low-light detection, lidar

Schottky

Metal-semiconductor junction, UV-sensitive

UV detection

 

3. Key Parameters of Photodiodes

Responsivity: Current generated per unit optical power (A/W).

 

Capacitance: Impacts high-frequency performance (pF level).

 

Reverse Breakdown Voltage: Determines the operating voltage range (5-300V).

 

4. What are the Typical Applications of Photodiodes?

Consumer Electronics: Mobile phone ambient light sensors, under-screen fingerprint recognition.

 

Industrial Inspection: Barcode scanning, color sensors.

 

Medical Equipment: Oximeters, medical imaging.

 

Automotive Electronics: Automatic headlight control, LiDAR systems.

 

Communication Systems: Core components at the optical fiber receiving end.

 

5. Selection Recommendations for Photodiodes

Select semiconductor materials (silicon/germanium/InGaAs) that match the spectrum;

 

For high-speed applications, prioritize PIN or APD structures;

 

Focus on noise equivalent power (NEP) in low-light environments;

 

Be aware of the impact of temperature on dark current.

 

6. Technology Trends of Photodiodes

Miniaturization: MEMS process integration.

 

Broad-spectrum Response: Application of new materials (such as graphene).

 

Intelligent Integration: Smart photodiodes with built-in amplification circuits.

 

Quantum dot Technology: Improves infrared response efficiency.