Temperature and doping-dependent interplay between the direct and indirect optical response in buffer-mediated epitaxial germanium

Lattice matched GeSn/InAlAs heterostructure: role of Sn in energy band alignment, atomic layer diffusion and photoluminescence

“…The peaks identified at 0.762 eV and 0.683 eV are from respective G-lh/hh and L-lh/hh transitions in the Ge layer. This is confirmed by the PL spectral peak positions in epitaxial Ge of sample A at 77 K, 46 where the G-valley was 0.11 eV above the L-valley. Whereas the other two peaks, located at 0.72 eV and 0.66 eV, are attributed to the photoemission peaks from the G-hh and L-hh transitions in the lh-hh degeneracy split (hh above lh) B0.81% compressively strained epitaxial GeSn layer.…”

“…The analysis showed shifts in the radiative (direct, G) and nonradiative (indirect, L) transition energies due to 6% Sn in GeSn compared to epitaxial Ge layer of sample A. 46 Also, the compressive strain induced blue shifts in the Ge 0.94 Sn 0.06 emission peaks from G-valley were observed, which asserted the need of a lattice matched GeSn/InAlAs material system.…”