We experimentally determine a spin-dependent band-gap renormalization of 60 $\mu$eV, and the hole spin relaxation dynamics in highly excited, strained Ge/SiGe quantum wells using a differential pump-probe technique which exploits the indirect nature of the band structure. Compressive strain lifts the degeneracy between heavy- and light-hole subbands, and both are addressed individually with our spectrally and polarization-resolved approach. We calculate that in our quantum wells, contrary to bulk Ge, we excite almost pure spin eigenstates so that a hole spin polarization exceeding 80$\%$ is obtained. A hole spin relaxation time of 2.1 ps is observed at 10 K.

• Received 20 February 2012

DOI:https://doi.org/10.1103/PhysRevB.85.241303