Ge1-xSnx/Si1-ySny SLs lattice-matched to Ge for 1.55 μm lasers

Abstract

GeSn is a promising material for fabricating light sources on Si integrated circuits. Because the lattice constant of GeSn is larger than that of Ge, GeSn lasers are grown on relaxed GeSn buffers or Ge virtual substrates, with edge dislocations in the interfaces. A structure of Ge1-xSnx/Si1-ySny SLs lattice-matched to Ge is proposed to overcome this drawback. Band structure was calculated with different Sn contents and thicknesses of GeSn and SiSn. Light emission at 1.55 μm was achieved with 0.9 nm GeSn0.11/ 3.9 nm SiSn0.195 SLs. A graded-index separate-confinement heterostructure laser was designed with the proposed SLs of 8 periods and its performance was investigated. The TE modal gain was dominant over TM modal gain, due to the top valence band is heavy hole-like. The transparency and threshold current density was 3.2 kA/cm2 and 4.1 kA/cm2, respectively at room temperature. This study provided a feasible way to fabricate CMOS compatible light sources monolithically integrated on Si platform.