Trion-Engineered Multimodal Photo-Transistors in Two-Dimensional Lateral Heterostructures

Journal article, 2025

Multimodal device operations are essential to advancing the on-chip integration of 2D semiconductors in electronics, photonics, and quantum technology. Precise control over carrier dynamics, particularly exciton generation and transport, is crucial for fine-tuning the functionality of 2D heterostructure-based optoelectronic devices. However, traditional exciton engineering in 2D semiconductors is mainly restricted to artificially assembled vertical heterostructures with electrical or strain-induced confinements. Here, bilayer 2D MoSe2-WSe2-MoSe2 lateral heterostructures are utilized to achieve preferential exciton generation and manipulation without the need for external confinement. In lateral n-p-n field-effect transistor (FET) geometry, unique and nontrivial electro-optical properties are uncovered, including dynamic tuning of channel photoresponsivity from positive to negative. The multimodal operation of these 2D-FETs is achieved by adjusting electrical bias and the impinging photon energy, enabling precise control over the trion generation and transport. Cryogenic photoluminescence measurement reveals the presence of trions in bilayer MoSe2 and intrinsic trap states in WSe2, which enhance the sensitivity of the device to near-infrared photons. Measurements in different FET device geometries show the multi-functionality of 2D lateral heterostructures for efficient electrical manipulation of excitonic characteristics. The findings pave the way for developing practical exciton-based transistors, sensors, multimodal optoelectronic components on-chip, and quantum technologies.