MBE growth, structural and transport properties of alternately-strained ZnSSe/CdSe superlattices with effective band-gap 2.5-2.6 eV

Short-period ZnSySe1−y/CdSe superlattices (SLs) with an effective energy gap Eg=2.5-2.6 eV (T=300 K) are grown by molecular beam epitaxy pseudomorphically on GaAs (001), and their structural properties are studied by using X-ray diffraction (XRD) and transmission electron microscopy. Both sulfur content and thickness of the ZnSySe1−y SL barriers have been determined via analysis of the XRD curves, taking account of the thickness of the CdSe SL layers estimated independently from the low-temperature (T=77 K) PL spectra of the single CdSe quantum dot (QD) layer (nominal thickness of 2.8 monolayer) embedded into each SL. The evaluated SL parameters are shown to be in good agreement with the intended ones. The efficient non-equilibrium carrier transport in the SLs along the growth direction at 300 K is demonstrated by photoluminescence (PL) spectroscopy through the relative temperature variation of the intensities of the PL peaks originated from the buried CdSe/ZnSe QD layers and the ZnSSe/CdSe SLs.