Raman scattering and photoluminescence studies of two-dimensional electron systems in Ge/GaAs heterostructures

Resonant Raman scattering experiments on n-Ge/n-GaAs (100) heterostructures reveal transitions involving quasi-two-dimensional electron states in Ge-accumulation layers. The experiments were performed in the range of the E₁-gap of Ge. The electronic scattering transforms into E₁-luminescence as the laser energy is tuned above the resonance. Spectra obtained at higher excitation energies show luminescence bands associated with the E₁ and E₁ + Δ₁-gap of Ge. The latter results are compared with recent data for bulk heavily-doped Ge.