Ultrabroadband and High-Detectivity Photodetector Based on WS₂/Ge Heterojunction through Defect Engineering and...

Area of Science:

• Optoelectronics and Nanomaterials Science
• Advanced Photodetector Technology

Background:

• Broadband photodetectors are crucial for various optoelectronic applications.
• Two-dimensional (2D) tungsten disulfide (WS2), a transition-metal dichalcogenide (TMD), shows promise for photodetection but faces limitations due to its large bandgap and interface recombination.

Purpose of the Study:

• To fabricate a high-sensitivity, ultrabroadband WS2/Ge heterojunction photodetector.
• To overcome the limitations of WS2 for broadband photodetection through defect engineering and interface passivation.

Main Methods:

• Fabrication of a WS2/Ge heterojunction photodetector.
• Defect engineering to narrow the WS2 bandgap via vacancy defects.
• Interface passivation using an ultrathin AlOx layer and construction of a vertical n-n heterojunction.

Main Results:

• The WS2/AlOx/Ge photodetector achieved high responsivity (634.5 mA/W) and specific detectivity (4.3 × 10^11 Jones).
• Demonstrated an ultrafast response speed.
• Achieved an ultrawide spectral response from 200 nm (deep UV) to 4.6 μm (mid-wave infrared), surpassing previous WS2 and TMD-based photodetectors.

Conclusions:

• The developed WS2/AlOx/Ge photodetector offers excellent performance for ultrabroadband detection and MWIR imaging at room temperature.
• The strategy of defect engineering and interface passivation provides a viable route for creating high-performance broadband photodetectors using 2D TMD materials.