Fast and efficient Sb-based type-II phototransistors integrated on silicon

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• On-chip photodetectors are crucial for optical interconnects in computing and sensing.
• Heterojunction phototransistors (HPTs) offer high energy efficiency but have limited gain-bandwidth product (GBP) compared to avalanche photodiodes at low optical powers.

Purpose of the Study:

• To enhance the GBP and energy efficiency of phototransistors for dense optical interconnects.
• To demonstrate the benefits of type-II energy band alignment in Sb-based HPTs.

Main Methods:

• Fabrication of Sb-based HPTs utilizing type-II energy band alignment.
• Integration of type-II HPTs with silicon photonic waveguides.
• Characterization of device performance, including junction capacitance, GBP, dark current, and energy consumption.

Main Results:

• Type-II HPTs exhibited a six-fold reduction in junction capacitance per unit area.
• Achieved a GBP comparable to avalanche photodiodes (∼270 GHz) at low optical powers.
• Demonstrated one order of magnitude better energy efficiency than avalanche devices, consuming 5 fJ/bit at 3.2 Gbps with a low error rate.

Conclusions:

• Type-II band alignment in Sb-based HPTs significantly improves performance for optical interconnects.
• These highly efficient and compact photodetectors enable new possibilities for optical receivers.
• The developed HPTs are suitable for dense optical interconnects in emerging computational and sensing applications.