Modulation of electronic and transport properties of bilayer heterostructures: InSe/MoS2 and InSe/h-BN as the prototype

Despite having the fascinating physical, electronic, and optical properties of two-dimensional (2D) crystals of ${\mathrm{MoS}}_{2}$, $h$-BN, and InSe, none of them solely meet all the desired criteria required for high efficiency optoelectronic devices, such as a suitable band gap with very high carrier mobility, a moderate excitonic lifetime, a desirable bending modulus, environmental stability against air and water, etc. Herein, we demonstrate that these fundamental limitations can easily be overcome by building a van der Waals heterostructure (vdW-HS) of monolayer InSe either with single-layer ${\mathrm{MoS}}_{2}$ or $h$-BN. Our first-principles calculations suggest that compared to individual monolayers, the examined $\mathrm{InSe}/{\mathrm{MoS}}_{2}$ and $\mathrm{InSe}/h$-BN vdW-HSs are not only thermodynamically and mechanically more robust but also possess improved electronic and optical properties, which can be particularly useful for solar harvesting devices. Importantly, through a systematic study, we elucidate that the band gap and its nature can largely be modulated ($\ensuremath{\sim}0.1--1.6$ eV, indirect $\ensuremath{\rightleftharpoons}$ direct, type I $\ensuremath{\rightleftharpoons}$ type II) for both the examined heterobilayers by applying mechanical strain and transverse electric field. Even more interestingly, we further show that with such bilayer heterostructures it is possible to get electron and hole mobility almost in the same order of magnitude (${10}^{3}$--${10}^{4}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$), either naturally or by applying small biaxial strain.