van der Waals Epitaxial Growth of Centimeter-Scale CdTe Thin Films for High-Performance Photodetectors

Group II–VI semiconductor CdTe is widely used in optoelectronic devices because of its high absorption coefficient and good chemical stability. High-quality CdTe thin films serve as the foundation for high-performance optoelectronic devices. In this work, centimeter-scale CdTe thin films were synthesized via van der Waals heteroepitaxy on mica substrates using vapor phase transport (VTD), and planar structure photodetectors (PDs) were constructed via depositing the Au electrodes on the surface directly or exfoliated buried interface. The results show that the performance of PDs constructed using a CdTe buried interface is much better than those constructed using a CdTe surface under the light irradiation at the wavelengths of 406, 642, and 808 nm, and the switching ratio can reach up to 2 × 10⁴, with a response of 4.4 A/W and a short response time of 1.5 ms. The smooth interface morphology and a large area of flat and dense surfaces are conducive to carrier transport, showing better performance. Furthermore, flexible PDs are constructed via transferring CdTe thin films onto a poly(ethylene terephthalate) (PET) substrate and exhibit excellent flexibility and stability, which can maintain 96.5% original performance with more than 200 times bending at a curvature radius of 5 mm. The research indicates that the high-quality, centimeter-scale CdTe with buried interface fabricated via van der Waals epitaxial growth is a promising potential candidate in high-performance optoelectronic devices.