Lattice strain and band offsets determination in ZnSe/ZnS short-period superlattices grown by MOVPE on (100)GaAs

We report a detailed calculation of the effects of residual lattice and thermal strains on the electronic states of nearly pseudomorphic ZnSe/ZnS short-period superlattices (SLs). Comparison is made with experimental electronic transitions derived from 10K absorption spectroscopy measurements performed on 30 periods ZnSe/ZnS SLs, having well and barrier thickness Lw=1.4 nm and Lb=5.7 nm, respectively. ZnSe/ZnS SLs were grown by metalorganic vapour phase epitaxy (MOVPE) on a 500 nm thick ZnS buffer layer and capped with a 210 nm thick ZnS epilayer. The whole structures were deposited on (100)GaAs. The intrinsic conduction to valence band offset ratio is finally found to be 8:92 for the above SL structure. The impact of the weak electron confinement on the SLs optical and electronic properties, with special attention to laser applications, is also discussed.