Tunable Electronic and Optoelectronic Properties in Low-Dimensional Noncentrosymmetric Tellurium Nanostructures

Low-dimensional noncentrosymmetric tellurium (Te) nanostructures exhibit huge potential for integrated electronics and optoelectronics because of their unique spiral chain structure, high carrier mobilities, and broadband photoresponse. However, there is still a lack of a basic understanding of size- and shape-dependent band structures, electrical transport, and optoelectronic properties in Te nanostructures, significantly limiting their device applications. Here, we perform a detailed theoretical investigation to reveal the size and surface effects on the electronic structures, optical absorption, carrier transport, and photoresponse of various types of Te nanosheets and nanowires using density functional theory calculations combined with the nonequilibrium Green’s function method. We demonstrate that these Te nanostructures exhibit a tunable bandgap in the range of 0.37–1.81 eV by the control of their size or layer thickness, suggesting they are ideally suitable as the channel materials for scaled electronic devices. Moreover, the noncentrosymmetric spiral chain structure in these Te nanostructures gives rise to an intrinsic electric polarization field, resulting in spontaneous charge carrier separation. Benefiting from the enhanced optical absorption (>105 cm–1) and bandgap narrowing, the increase of size or layer number in these Te nanostructures not only greatly promotes the photocurrent but also induces the increase of dark current, which offers a large flexibility to tailor their band structures and optoelectronic properties for various optoelectronic applications, such as photodetectors and solar cells.