Growth of Znx, Cd_(1-x′) Se/ Zn_x Cd_y Mg(_1-x-y) Se-InP quantum cascade structures for emission in the 3-5 μm range

The molecular beam epitaxial growth and electroluminescence (EL) properties of Zn_0.48 Cd_0.52 Se/ Zn_0.24 Cd_0.18 Mg_0.58 Se quantum cascade (QC) structures are reported. The samples were composed of 30 repeats of a three-well active region. Cladding layers were inserted to isolate the core of the EL structure from the heavily doped contact region and to obtain optical confinement. Electroluminescence was observed in the 4-5 μm range. The observed narrowing of the electroluminescence linewidth was tentatively attributed, in part, to the incorporation of the ZnCdMgSe waveguide layers. A test sample consisting of multiple asymmetric coupled quantum well active regions separated by quaternary barrier layers was also investigated. The Fourier transform infrared (FTIR) absorption spectroscopy measurements suggest that QC structures with EL emission in the 3-4 μm range can be achieved with these materials.