Photoluminescence properties of heavily Sb doped Ge1-xSnxand heterostructure design favorable for n+-Ge1-xSnxactive layer

We investigated the photoluminescence (PL) properties of heavily Sb doped n+-Ge1-xSnxlayers and demonstrated the formation of a double heterostructure (DHS) for the n+-Ge1-xSnxactive layer. A single PL peak was observed for n+-Ge1-xSnxlayers thicker than 80 nm with increasing the Sb concentration up to 1020cm-3, attributed to the superior crystallinity and pseudo-direct bandgap transition mechanism, while a 15 nm thick n+-Ge1-xSnxlayer did not exhibit PL signals. A favorable heterostructure for n+-Ge1-xSnxis proposed from the viewpoint of the increased valence band offset (?Ev) using n-SiyGe1-yas the cladding layer. We demonstrated the formation of an n-SiyGe1-y(15 nm)/n+-Ge1-xSnx(15 nm)/n-SiyGe1-y(15 nm) DHS with a superior crystallinity and high PL peak intensity comparable to that of a thick n+-Ge1-xSnx. We discuss the reasons for the PL performance improvement by forming the DHS, including the sufficient carrier confinement and the suppression of surface recombination.