Synthesis of lateral heterostructure of 2D materials for optoelectronic devices: challenges and opportunities

In the increasing demands for exotic device development in the fields of electronics, optoelectronics, sensors, energy, integrated circuits, and quantum technologies, 2D heterostructures can offer tremendous possibilities to sustain Moore's law. Despite considerable efforts in integrating distinct 2D materials, incomplete understanding of the role of native defects, poor mobility, stability, and low quantum yield poses many challenges for the overall performance of most heterostructure-based devices. In this review, we explore the recent development in the synthesis, strategies for interface modulation, structure-property optimization, and nanofabrication technologies of 2D lateral assembly. Specifically, chemical vapor deposition (CVD) methods and adopting phase and doping engineering for the reliable development of lateral heterostructures are explored in detail. The traditional phase engineering is extrapolated to understand the role of metal/2D semiconductors contact interface, essentially bridging metallic 2D materials as contacts to traditional metal electrodes. The applications of these integrated 2D lateral heterostructures as an active component of many optoelectronics including p-n junction diodes, high-performance transistors, LED, photosensors, and photovoltaics are highlighted. Moreover, we underline the challenges and outlooks to increase the library of 2D lateral geometry in high phase purity and excellent controllability.