Emergent Fabry-Pérot Interference for Light-Matter Interaction in van der Waals WS 2 /SiP 2 Heterostructures.

Fabry-Pérot interference plays an important role in modulating the spectral intensity of optical response originating from light-matter interactions. Examples of such interference occurring in the substrate as the resonating cavity have been demonstrated and probed by two-dimensional layered materials. Similarly, the Fabry-Pérot interference can occur and modulate the optical response in the heterostructure; however, this remains elusive. Herein, we observe the Fabry-Pérot interference on photoluminescence (PL) and Raman spectra in monolayer WS 2 /SiP 2 heterostructures by varying the thickness of bottom SiP 2 from 2 to 193 nm, which serves as the Fabry-Pérot cavity. Both the intensities of the PL spectra and the E 2g 1 Raman mode of WS 2 /SiP 2 heterostructures first decrease to almost zero while displaying an interference increase at a SiP 2 thickness of 75 nm. Our findings clearly demonstrate the Fabry-Pérot interference in the optical response of heterostructures, providing crucial information to optimize the optical response and paving the way toward photodetector applications.