Abstract
We have measured the dependence on pressure of the low-temperature (10 K) direct exciton optical absorption of Ge up to 12.3 GPa. The sharp exciton peak at the direct energy gap () of Ge is found to broaden significantly with increasing pressure. This effect, which is attributed to intervalley scattering via electron-phonon interaction, is most pronounced for pressures above ∼0.6 GPa, where the X valley becomes the lowest conduction-band minimum. From the pressure-induced exciton broadening we determine the Γ to X point intervalley deformation-potential constant =2.2(3) eV/Å and an upper bound of =4.5 eV/Å for scattering from Γ to the L valleys. The deformation potential of Ge is about 50% smaller compared to isoelectronic GaAs. This difference is attributed to the fact that interatomic matrix elements between s and d states of the Γ and X conduction-band minima as well as the d character of the X minimum are larger in GaAs.
- Received 22 November 1993
DOI:https://doi.org/10.1103/PhysRevB.49.8017
©1994 American Physical Society