Two-dimensional (2D) transition metal dichalogenides exhibit a unique band structure: In contrast to many direct-gap classical semiconductors, their band-gap minimum is not at the center of the Brillouin zone, but at finite values of the $k$ vector. We report on clear indications that this momentum mismatch fundamentally influences the carrier transfer between a 2D ${\mathrm{WS}}_2$ crystal and a three-dimensional (3D) GaN layer: Populating different local band extrema of the ${\mathrm{WS}}_2$ in $k$ space by selective laser excitation leads to a pronounced difference in the ${\mathrm{WS}}_2$ photoluminescence signal. These findings may be of high importance for future 2D-3D semiconductor devices.

• Received 24 November 2016

DOI:https://doi.org/10.1103/PhysRevB.95.081304