Optically Allowed Photoluminescence from a Direct-Gap Si-Ge Superstructure on Si0.4Ge0.6

David J. Lockwood (1) , Nelson L. Rowell (1) , Adrien Gouyé (2) , Luc Favre (2) , Antoine Ronda (2) , Isabelle Berbezier (2)

1 Measurement Science and Standards [Ottawa]
2 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

Both Si and Ge possess an indirect band gap, which makes them very inefficient light emitters, and band gap engineering has been proposed as a way to overcome this limitation. According to the theoretical work of M. d’Avezac et al. (Phys. Rev. Lett. 108, 027401 (2012)), a SiGe2Si2Ge2SiGen superstructure on Si0.4Ge0.6 should have a direct and dipole-allowed gap of 0.863 eV. Here we report on the growth of such a structure and its optical properties. Two similar samples were prepared by molecular-beam and solid-phase epitaxy. Photoluminescence (PL) spectra were obtained at low temperatures (6-25 K) with excitation at 405 and 458 nm. A strong low-energy PL quadruplet is seen, with peaks near 729, 758, 792 and 823 meV at 6 K, together with a much weaker peak at 871 MeV. The weak peak at 871 meV is assigned to the dipole-allowed direct-gap transition expected in the superstructure.

Domaines: Matière Condensée [cond-mat]

David J. Lockwood, Nelson L. Rowell, Adrien Gouyé, Luc Favre, Antoine Ronda, et al.. Optically Allowed Photoluminescence from a Direct-Gap Si-Ge Superstructure on Si0.4Ge0.6. ECS Transactions, 2014, 61 (5), pp.31--36. ⟨10.1149/06105.0031ecst⟩. ⟨hal-01811405⟩