Generation of terahertz radiation from the island films of topological insulator Bi2-xSbxTe3-ySey

The aim of the research was the studying of the topological insulators Bi2-xSbxTe3-ySey thin films with the different thickness and chemical composition. The obtained time dependences of terahertz radiation have indicated that the generation of THz waves was more efficient in the island film having a total thickness of about tens nanometers with the composition close to the Ren’s curve, where the volume contribution to the conductivity was suppressed. We have demonstrated an amplification of the THz radiation power by applying an external electric field to a topological insulator. This effect can be useful for fabricating photoconductive THz antennas based on topological insulators

Free Exciton Luminescence in ZnCdSe Solid Solutions, ZnSe Epitaxial Films and ZnSe1−x\text{}_{1-x}Sx\text{}_{x}/ZnSe1−y\text{}_{1-y}Sy\text{}_{y} Superlattices

We studied the luminescence of bulk Zn$\text{}_{1-x}$Cd$\text{}_{x}$Se solid solutions, epitaxial ZnSe films and ZnSe$\text{}_{1-x}$S$\text{}_{x}$/ZnSe$\text{}_{1-y}$S$\text{}_{y}$ superlattices at T=2-80 K. The analysis of the bands of exciton radiative annihilation with simultaneous emission of 1 or 2 LO phonons shows that the excitons in the studied samples can be considered as free particles with thermalized distribution of kinetic energies. In ZnSe$\text{}_{1-x}$S$\text{}_{x}$/ZnSe$\text{}_{1-y}$S$\text{}_{y}$ superlattices a three-dimensional character of exciton motion was established. The periodic potential of superlattice perturbs the exciton wave vector and induces additional elastic scattering of excitons

MOCVD growth and characterisation of ZnS/ZnSe distributed Bragg reflectors and ZnCdSe/ZnSe heterostructures for green VCSEL

High reflectivity ZnS/ZnSe distributed Bragg reflectors (DBR) have been grown on GaAs(100) substrates using metallorganic chemical vapour deposition technique. It was found that the surface roughness, which limits the ZnS/ZnSe DBR mirror reflectivity, may be reduced using the interruption of chalcogen-contained flow before each successive layer growth. The DBR mirrors have been obtained with reflectivity as high as 99% and 94% at the wavelengths of 478 nm and 520 nm, respectively. The ZnCdSe/ZnSe QW structure grown on the ZnS/ZnSe DBR mirror manifests cathodoluminescence at room temperature whose intensity is an order of magnitude less than that of the similar structure grown on ZnSe buffer. Large lattice mismatch between ZnS and ZnSe layers results in high density of defects in ZnCdSe/ZnSe QW structures grown on. the DBR

Non-rigid alignment for temporally consistent 3D video

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