MOVPE of ZnMgSSe heterostructures for optically pumped blue-green lasers

Abstract

We report on the growth of ZnMgSSe/ZnSSe/ZnSe heterostructures in a low pressure metalorganic vapor phase epitaxy (MOVPE) system at 400 hPa and a growth temperature of 330°C. The precursor combination was dimethylzinc(triethylamine adduct), ditertiarybutylselenium, ditertiarybutylsulphur, and bismethylcyclopentadienylmagnesium. This combination allows the reproducible adjustment of the alloy composition in a wide range (currently up to 40% S and 32% Mg) maintaining high crystal homogeneity and almost lattice matched growth. Undoped separate confinement heterostructure (SCH) lasers with ZnMgSSe cladding and ZnSSe guiding layers were deposited on GaAs substrates. X-ray diffraction (reciprocal space mapping), photoluminescence (PL) at 14–300K, PL excitation, and optical pumping experiments were performed. The quantum wells show a high luminescence efficiency up to room temperature. Optical pumping experiments were carried out at various temperatures (77, 300–375K) and excitation densities using a nitrogen laser. The lasing threshold could be determined to be less than 20 kW/cm2 at 77K, and even room temperature lasing was observed at an excitation density which was below 200 kW/cm2.