A design and method to create superlattices, alternating stacks of two-dimensional materials and semiconductors to obtain strong light absorption. 

Next-generation optical technologies like light detection and ranging (LiDAR) and on-chip optical modulators have wide-ranging applications in autonomous vehicles, device communication, and computing. Unfortunately, existing technologies are hampered by their sensitivity, often requiring specific substrates and operating environments. Two-dimensional materials like transition metal dichalcogenides (TMDs) have highly desirable optical and electronic properties for such applications, but offer uneven sample thickness, small lateral dimensions, and weak light absorption. 

The researchers developed a method to create semiconductor-TMD superlattices. These superlattices offer controllable thickness, device-scale lateral size, and strong light absorption. In addition, they maintain the quantum effects found in TMD monolayers such as exciton-polariton splitting. This introduces exciting avenues for optical device engineering. 

TMDs offer an excellent platform for optical devices due to their direct bandgap, strong quantum confinement, and nonradiative exciton-hole energy loss. The authors were inspired by these benefits to devise a method to harness TMDs’ upsides while mitigating the downsides of sample preparation and geometry. They accomplished this by stacking TMDs and thin semiconductors together using a wet chemical transfer process. This stabilizes the TMDs and enables quantum device designs on the order of square centimeters. 

• Method creates samples on the order of 1 cm2 for real-world device applications
• Superlattices exhibit over 80% light absorption at TMD excitonic frequency
• Preserves quantum effects of the monolayer TMDs, including exciton-polariton Rabi splitting up to 170 meV
• Cavity mode quality factor as large as 300
• Operates at room temperature