Intense photoluminescence from Ge(Si) self-assembled islands embedded in a tensile-strained Si layer

Photoluminescence (PL) of structures with Ge(Si) self-assembled islands located between tensile-strained Si layers grown on smooth strain-relaxed Si1-xGex/Si (001) (x = 0.2 - 0.3) buffer layers has been studied. The peak observed in the PL spectra of the structures studied is associated with indirect optical recombination of electrons confined in strained Si layers on the heterojunction with islands and holes localized in Ge-rich islands. The redshift of the PL peak with an increase in the strained Si layer thickness confirms the validity of the proposed optical transition. The intensity of the PL signal from Ge( Si) islands located between tensile-strained Si layers at 77 K is one order of magnitude higher than the PL signal from Ge(Si) islands grown on unstrained Si (001) substrates. The substantial rise of the PL signal is associated with efficient quantum confinement of electrons in the strained Si layer on the heterojunction with Ge(Si) islands.