Defect density reduction in core layer of ZnTe electro-optical waveguide by low lattice mismatched interfaces

Abstract

ZnTe electro-optic waveguide device has a great potential for the practical applications. The introduction of low Mg% cladding layer to the ZnMgTe/ZnTe/ZnMgTe waveguide structure was performed to circumvent the effect of large lattice mismatch between ZnMgTe and ZnTe, and to improve the crystallographic properties. Various two-step index ZnTe waveguide structures were fabricated by molecular beam epitaxy. The structure with 0.1 μm (Mg 9%) interlayer and 0.6 μm (Mg 26%) cladding layer showed significant defect density reduction compared to the single-step index ZnTe waveguide (Mg 20%) due the much smaller lattice mismatch between the ZnTe core layer and the ZnMgTe interlayer. However, the average Mg content of ZnMgTe layers needs to be carefully controlled to prevent the drop of the optical confinement.