Large area van der Waals epitaxy of II–VI CdSe thin films for flexible optoelectronics and full-color imaging

The demand for future semiconductor devices with enhanced performance and lower cost has driven the development of epitaxial growth of high quality, free-standing semiconductor thin film materials without the requirement of lattice matching to the substrate, as well as their transfer to other substrates and associated device processing technology. This work presents a study on the van der Waals epitaxy based molecular beam epitaxy of CdSe thin films on two-dimensional layered mica substrates, as well as related etch-free layer transfer technology of large area, free-standing layers and their application in flexible photodetectors for full-color imaging. The photoconductor detectors based on these flexible CdSe thin films demonstrate excellent device performance at room temperature in terms of responsivity (0.2 A·W−1) and detectivity (1.5 × 1012 Jones), leading to excellent full-color imaging quality in the visible spectral range. An etch-free and damage-free layer transfer method has been developed for transferring these CdSe thin films from mica to other substrate for further device processing and integration. These results demonstrate the feasibility of van der Waals epitaxy method for growing high quality, large area, and free-standing epitaxial layers without the requirement for lattice matching to substrate for applications in low-cost flexible and/or monolithic integrated optoelectronic devices.