High responsivity SiGe heterojunction phototransistor on silicon photonics platform

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• Standard silicon photonics foundries offer a scalable platform for fabricating optoelectronic devices.
• Phototransistors are crucial components in optical sensing and communication systems.
• Near-infrared (NIR) detection is essential for various applications, including telecommunications and imaging.

Purpose of the Study:

• To report on the fabrication and characterization of a novel near-infrared silicon-germanium (SiGe) phototransistor.
• To investigate the performance of the SiGe phototransistor through simulations and experimental measurements.
• To propose a differential detection scheme for enhancing device sensitivity.

Main Methods:

• Device simulation using standard foundry processes.
• Fabrication of SiGe phototransistors.
• Electrical characterization (current-voltage measurements) under varying optical power.
• Implementation and testing of a differential detection scheme for dark current cancellation.

Main Results:

• The fabricated SiGe phototransistors demonstrate high responsivity at 1.55µm wavelength.
• Record responsivity exceeding 232 A/W at 5V bias and 42 A/W at 1V bias was achieved at low optical power.
• The proposed differential detection scheme effectively cancels dark current, significantly increasing device sensitivity.

Conclusions:

• A novel NIR SiGe phototransistor has been successfully fabricated using a standard silicon photonics foundry.
• The device exhibits excellent responsivity, making it suitable for high-performance optical detection.
• The differential detection scheme offers a viable method for enhancing phototransistor sensitivity in practical applications.