Injection spin-Hall effect in a GeSn/Ge two-dimensional hole gas

The investigation of spin-orbit coupling in novel GeSn alloys offers the unique possibility to control the system Hamiltonian by virtue of strain and bandgap engineering. Such a capability provides radically new possibilities to implement spin-dependent functionalities beyond the very rich spin physics of Ge. In this work, we use optical spin orientation to generate a spin current. We investigate the spin dynamics of p-type modulation doped QWs realized by embedding GeSn layers within barriers of elemental Ge. The formation of a two-dimensional hole gas (2DHG) at cryogenic temperatures is observed through transport, while magneto-photoluminescence enables the determination of the spin lifetime by means of the Hanle effect. Finally, spin-to-charge interconversion of the optically generated spin current manifests itself under an applied electric field via the inverse spin-Hall effect, and demonstrates an efficiency increase of more than one order of magnitude compared to bulk Ge. Such finding, along with the notable coupling between spin states and light fields, makes GeSn/Ge 2DHG a prominent candidate at the leading edge between spintronic and photonic quantum technologies.