Van der Waals Epitaxy of HgCdTe Thin Films for Flexible Infrared Optoelectronics

Van der Waals epitaxial (vdW) growth of semiconductor thin films on 2D layered substrates has recently attracted considerable attention since it provides a potential pathway for realizing monolithically integrated devices and flexible devices. In this work, direct growth of epitaxial HgCdTe (111) thin films on 2D layered transparent mica substrates is achieved via molecular beam epitaxy. The full width at half maximum of the ω-mode X-ray diffraction peak is measured to be around 306 arc sec. Mid-wave infrared photoconductors based on the as-grown HgCdTe thin films have been demonstrated and the self-heating effect has been evaluated. A peak responsivity at the wavelength of around 3500 nm is measured to be about 110 V W⁻¹ at 80 K and 8 V W⁻¹ at room temperature under a bias of 25 V cm⁻¹. Twinning defects are observed, limiting the crystallinity and mobility-lifetime product in HgCdTe/mica. Benefiting from the vdW epitaxial growth, an etch-free layer transfer process for lifting off the HgCdTe from the mica substrate has been demonstrated, leading to large area free-standing HgCdTe thin films.