Low-threshold green laser heterostructures with Zn(Mg)SSe/ZnSe graded-index superlattice waveguide: Structural and optical properties

Abstract

We report on structural and optical properties of green (λ∼520 nm) ZnCdSe/ZnMgSSe optically pumped laser heterostructures with a Zn(Mg)SSe/ZnSe graded-index superlattice (SL) waveguide, grown by molecular beam epitaxy. The pseudomorphic 400 nm thick waveguide comprising a set of strained ZnMgSSe/ZnSe and ZnSSe/ZnSe SLs of different periods and barrier-to-well thickness ratios at each side of a ZnCdSe quantum well (QW) active region provides efficient transport of nonequilibrium carriers to the QW. This results in reduction in laser threshold down to the extremely low value of 1.5 kW/cm2 at 300 K and increasing the external quantum efficiency above 44%.