Focus on the Avalanche Breakdown Characteristic of Si- and InP-Based APDs Irradiated by Fast Neutrons

Area of Science:

• Materials Science
• Semiconductor Physics
• Radiation Effects

Background:

• Silicon (Si) and Indium Phosphide (InP) avalanche photodiodes (APDs) are critical for weak light detection in irradiation environments.
• Understanding neutron irradiation effects on these APDs is vital for their reliable application.

Purpose of the Study:

• To investigate the impact of neutron irradiation on the dark current and gain characteristics of Si- and InP-based APDs.
• To elucidate the mechanisms behind observed changes in APD performance post-irradiation.
• To identify design strategies for enhancing radiation resistance.

Main Methods:

• Detailed analysis of dark current and gain of Si- and InP-based APDs before and after neutron irradiation.
• Characterization of breakdown voltage shifts and breakdown behavior.
• Comparative study of irradiation effects based on APD material and structure.

Main Results:

• Both Si- and InP-based APDs showed increased dark current and decreased gain after neutron irradiation.
• Neutron-induced generation centers were identified as the cause of increased dark current.
• Si-based APDs experienced a significant reduction in breakdown voltage (~8 V) at 1.0 × 10^12 cm^-2 fluence.
• InP-based APDs showed a smaller breakdown voltage change (~1.5 V) at a higher fluence of 1.0 × 10^13 cm^-2.
• The p-doped multiplication layer in Si-APDs contributed to a greater breakdown voltage shift due to carrier removal effects.

Conclusions:

• Neutron irradiation degrades the performance of Si- and InP-based APDs by increasing dark current and reducing gain.
• The use of an intrinsic multiplication layer in APD design is recommended for improved neutron radiation resistance.
• Findings provide insights for radiation-hardened APD design and a deeper understanding of irradiation mechanisms.