Multilayer ReS₂ Photodetectors with Gate Tunability for High Responsivity and High-Speed Applications

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional semiconductors like rhenium disulfide (ReS2) are promising for photodetection due to their direct band gap.
• Existing studies often overlook the critical trade-off between responsivity and response time in photodetectors under varied conditions.

Purpose of the Study:

• To comprehensively investigate the impact of architecture, laser power, and gate bias on the performance of ReS2 phototransistors.
• To explore the tunability of responsivity and response time by manipulating trap states in ReS2.

Main Methods:

• Fabrication and characterization of supported and suspended ReS2 phototransistors.
• Systematic measurements of photocurrent, responsivity, and response time under varying laser power and gate bias.
• Analysis of trap state occupancy and its influence on device performance.

Main Results:

• Uniform photogeneration observed across ReS2 channels due to enhanced absorption and direct band gap.
• Achieved high responsivity (4 A W⁻¹) with a 50 ms response time and a fast response time (20 μs) with 4 mA W⁻¹ responsivity.
• Demonstrated four orders of magnitude tunability in response time and 15× tunability in responsivity via gate bias modulation.
• Identified distinct trap distributions in suspended versus supported ReS2, enabling switching between photogating and photoconduction mechanisms.

Conclusions:

• ReS2 phototransistors exhibit versatile and tunable photodetection capabilities, balancing high responsivity and fast response times.
• Gate bias modulation effectively controls trap occupancy, offering precise tuning of photodetector performance.
• A novel metric is proposed to evaluate intrinsic photodetector performance by considering the responsivity-speed trade-off, normalized for bias and geometry.