Anomalous Temperature Effect in Weakly Coupled Superlattices: Carrier Transport in a THz Quantum Cascade Laser.

We present an investigation into the vertical transport through 13 different superlattice structures, where the well and barrier widths, doping concentration, dopant position, and contact layers were varied. Although superlattices have been extensively studied since 1970, there is a lack of publications on transport through superlattices similarly low doped as THz quantum cascade lasers (QCLs), for which the doping is in the 3-5×10^{10}  cm^{-2} range. The superlattices presented are doped in the same range as THz QCLs, with contact layers and fabrication comparable to high-temperature THz QCLs.

Geometry of tellurene adsorbed on the Si(111)-30°-Sb surface from first principles calculations.

The 2D form of tellurium, named tellurene, is one of the latest discoveries in the family of 2D mono-elemental materials. In a trilayer configuration, free-standing tellurene was predicted theoretically to acquire two crystallographic forms, the and phases, corresponding to either a 1T-MoS-like geometry or a trilayer slab exposing the Te(101̄0) surface of bulk Te with helical chains lying in-plane and further reconstructed due to the formation of interchain bonds. Either one or the other of the two phases was observed experimentally to prevail depending on the substrate they were grown onto.