Zn irradiation effects in MBE growth of MgSe/BeZnSeTe II-VI compound superlattices on InP substrates

MgSe/BeZnSeTe II-VI compound superlattices (SLs) were grown on InP substrates by molecular beam epitaxy (MBE). In the growth, Zn molecular beam irradiation was performed at each hetero-interface between MgSe and BeZnSeTe layers to suppress in-plane compositional fluctuation of the BeZnSeTe layers and to enhance steepness of the interfaces. The Zn irradiation effect was systematically investigated changing the Zn irradiation time. As a result, it was found that structural and optical properties of the SLs strongly depended on the Zn irradiation time. Explicit high-order X-ray diffraction (XRD) satellite peaks appeared by introducing the Zn irradiation, which means the interface steepness was improved. In photoluminescence (PL) measurements at room temperature (RT), single peak emissions around 520 nm were observed. PL intensities at 15 K and RT strongly depended on the Zn irradiation time, and they were maximized when the Zn irradiation time was 4 s. The supply amount of the Zn irradiation for 4 s corresponds to about two-monolayer growth. From the dependencies of the PL intensity, it was shown that appropriate Zn irradiation was effective for both increase in the radiative recombination rate and decrease in the non-radiative recombination rate.