Search

The authors report the optimization of MgSe coupling layer thickness in MgSe/CdSe coupled quantum well (QW) structures and its effect on structural and optical quality as well as electron energy levels in the QWs. The structures were grown by molecular beam epitaxy with MgSe coupling layer thickness varying from 2 mono-layers (MLs), to 4 MLs. X-ray diffraction measurements showed that the thinner the MgSe coupling layer thickness the better the structural quality of the samples. Photoluminescence showed red shift of QW emissions with the decrease of MgSe coupling layer thickness, as a result of stronger coupling of electron states in samples with thinner coupling layers. While in the structures with thinner (2 MLs) coupling layers, the electron energy levels broadening may weaken the intersubband (ISB) transitions, the weak ISB absorption in samples with thicker (4 MLs) coupling layers are likely due to the poorer overall sample quality. Optimized MgSe coupling layer thickness is found to be around 3 MLs, with which a clear coupling effect is observed with ISB absorption around 1.55 μm.

A (Ga, Mn)As/GaAs superlattice, a semiconductor-based ferromagnetic/non-magnetic multilayer system, was prepared by low-temperature molecular beam epitaxy. X-ray diffraction measurements showed that the superlattice structure has high crystal perfection and good interface quality. Magnetotransport measurements revealed the presence of ferromagnetic order in the multilayer system at low temperatures.