Carrier transfer across a 2D-3D semiconductor heterointerface: The role of momentum mismatch

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 WS2 crystal and a three-dimensional (3D) GaN layer: Populating different local band extrema of the WS2 in k space by selective laser excitation leads to a pronounced difference in the WS2 photoluminescence signal. These findings may be of high importance for future 2D-3D semiconductor devices.