Optoelectronic properties of single-crystalline GaInAsSb quaternary alloy nanowires

Bandgap engineering of semiconductor nanomaterials is critical for their applications in nanoelectronics, optoelectronics, and photonics. Here we report, for the first time, the growth of single-crystalline quaternary alloyed Ga_(0.75)In_(0.25)As_(0.49)Sb_(0.51) nanowires via a chemical-vapor-deposition method. The synthesized nanowires have a uniform composition distribution along the growth direction, with a zinc-blende structure. In the photoluminescence investigation,these quaternary alloyed semiconductor nanowires show a strong band edge light emission at 1950 nm(0.636 e V). Photodetectors based on these alloy nanowires show a strong light response in the near-infrared region(980 nm) with the external quantum efficiency of 2.0 × 10~4% and the responsivity of 158 A/W. These novel near-infrared photodetectors may find promising applications in integrated infrared photodetection, information communication, and processing.     

Exciton luminescence and many-body effect of monolayer WS2 at room temperature

Monolayer transition metal dichalcogenides favor the formation of a variety of excitonic quasiparticles, and can serve as an ideal material for exploring room-temperature many-body effects in two-dimensional systems. Here, using mechanically exfoliated monolayer WS₂ and photoluminescence (PL) spectroscopy, exciton emission peaks are confirmed through temperature-dependent and electric-field-tuned PL spectroscopy. The dependence of exciton concentration on the excitation power density at room temperature is quantitatively analyzed. Exciton concentrations covering four orders of magnitude are divided into three stages. Within the low carrier concentration stage, the system is dominated by excitons, with a small fraction of trions and localized excitons. At the high carrier concentration stage, the localized exciton emission from defects coincides with the emission peak position of trions, resulting in broad spectral characteristics at room temperature.