2D SiP₂/h-BN for a Gate-Controlled Phototransistor with Ultrahigh Sensitivity

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials offer unique electronic and optical properties for advanced photodetectors.
• Current 2D photodetectors face challenges with high dark currents and low detectivity, limiting ultrasensitive applications.
• Developing photodetectors for extremely low-light levels remains a significant technological hurdle.

Purpose of the Study:

• To design and demonstrate a gate-controlled 2D phototransistor with ultrahigh sensitivity.
• To investigate the performance of silicon phosphide (SiP2) integrated with hexagonal boron nitride (h-BN) for photodetection.
• To address the limitations of dark current and detectivity in 2D material-based photodetectors.

Main Methods:

• Fabrication of a back-gated phototransistor device using 2D SiP2 and h-BN.
• Characterization of the phototransistor's electronic and optoelectronic properties, including dark current and photocurrent.
• Evaluation of device performance under varying gate voltages to assess responsivity and detectivity.

Main Results:

• The SiP2/h-BN phototransistor achieved an ultrahigh detectivity of 3.4 × 10^13 Jones.
• A gate-tunable responsivity up to 43.5 A/W was observed due to the photogating effect.
• The device exhibited significantly reduced dark current and enhanced photocurrent, leading to superior sensitivity.

Conclusions:

• The developed SiP2/h-BN phototransistor demonstrates one of the highest detectivities reported for 2D material-based photodetectors.
• The phototransistor configuration and h-BN substrate effectively suppress dark current and reduce charge scattering, enhancing performance.
• This work presents a promising strategy for advancing ultrasensitive optoelectronic applications using 2D materials like SiP2.