[en] Van der Waals heterostructures provide a versatile tool to not only protect or control, but also enhance the properties of a 2D material. We use ab initio calculations and semi-analytical models to find strategies which boost the mobility of a current-carrying 2D semiconductor within an heterostructure. Free-carrier screening from a metallic "screener" layer remotely suppresses electron-phonon interactions in the current-carrying layer. This concept is most effective in 2D semiconductors whose scattering is dominated by screenable electron-phonon interactions, and in particular the Fröhlich coupling to polar-optical phonons. Such materials are common and characterised by overall low mobilities in the small doping limit, and much higher ones when the 2D material is doped enough for electron-phonon interactions to be screened by its own free-carriers. We use GaSe as a prototype and place it in a heterostructure with doped graphene as the "screener" layer and BN as a separator. We develop an approach to determine the electrostatic response of any heterostructure by combining the responses of the individual layers computed within density-functional perturbation theory. Remote screening from graphene can suppress the long-wavelength Fröhlich interaction, leading to an almost constant mobility around 500 to 600 cm2/Vs for carrier densities in GaSe from 10^11 to 10^13 cm−2. Notably, the low-doping mobility is enhanced by a factor 3. This remote free-carrier screening is more efficient than more conventional manipulation of the dielectric environment, and it is most efficient when the separator (BN) is thin.
Disciplines :
Physics
Author, co-author :
Sohier, Thibault ; Université de Liège - ULiège > Département de physique > Physique des matériaux et nanostructures
Gibertini, Marco; Universita di Modena e Reggio Emilia > Fisica Informatica e Matematica
Verstraete, Matthieu ; Université de Liège - ULiège > Département de physique > Physique des matériaux et nanostructures
Language :
English
Title :
Remote free-carrier screening to boost the mobility of of Fröhlich-limited 2D semiconductors
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