Wafer-Scale Bandgap-Tunable MoS₂/PbS Phototransistors Enabled by Solution Processing.

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Molybdenum disulfide (MoS₂)/lead sulfide (PbS) heterostructures offer strong light-matter interactions and high carrier mobility.
• Bandgap engineering is crucial for optimizing light absorption in next-generation phototransistors.
• Conventional fabrication methods for MoS₂/PbS heterojunctions limit bandgap tunability due to vertical coupling.

Purpose of the Study:

• To realize wafer-scale, bandgap-tunable MoS₂/PbS phototransistors.
• To investigate the band structure of vertical and lateral MoS₂/PbS heterojunctions for bandgap tunability.
• To achieve wafer-scale uniformity and scalability in MoS₂/PbS heterojunction fabrication.

Main Methods:

• Ab initio calculations to study the band structure of vertical and lateral MoS₂/PbS heterojunctions.
• Investigation of plasma treatment to modulate thin-film surface energy for improved fabrication.
• Fabrication of MoS₂/PbS phototransistors on a 4-inch wafer scale.

Main Results:

• Lateral heterojunctions were found to dominate bandgap tunability by tuning the Type-II band alignment.
• Plasma treatment enabled scaling of MoS₂/PbS heterojunction fabrication to a 4-inch wafer scale with 97% yield.
• Achieved bandgap tunability from 1.24 eV to 0.61 eV, with phototransistors showing high responsivity (88 A/W), detectivity (4.77 × 10¹² Jones), and on/off ratio (3.16 × 10⁷).

Conclusions:

• Lateral MoS₂/PbS heterojunctions are key for achieving tunable bandgaps.
• Plasma treatment is an effective method for wafer-scale fabrication of uniform MoS₂/PbS heterojunctions.
• This work provides a pathway for developing wafer-scale, bandgap-tunable optoelectronic devices.