2D-GaN/AlN Multiple Quantum Disks/Quantum Well Heterostructures for High-Power Electron-Beam Pumped UVC Emitters.

This article describes GaN/AlN heterostructures for ultraviolet-C (UVC) emitters with multiple (up to 400 periods) two-dimensional (2D)-quantum disk/quantum well structures with the same GaN nominal thicknesses of 1.5 and 16 ML-thick AlN barrier layers, which were grown by plasma-assisted molecular-beam epitaxy in a wide range of gallium and activated nitrogen flux ratios (Ga/N*) on -sapphire substrates. An increase in the Ga/N* ratio from 1.

Indirect bandgap MoSe resonators for light-emitting nanophotonics.

Transition metal dichalcogenides (TMDs) are promising for new generation nanophotonics due to their unique optical properties. However, in contrast to direct bandgap TMD monolayers, bulk samples have an indirect bandgap that restricts their application as light emitters. On the other hand, the high refractive index of these materials allows for effective light trapping and the creation of high-Q resonators.

Nanoscale Electric Field Probing in a Single Nanowire with Raman Spectroscopy and Elastic Strain.

In this work we investigate the Raman response of extremely strained gallium phosphide nanowires. We analyze new strain-induced spectral phenomena such as 2-fold and 3-fold phonon peak splitting which arise due to nontrivial internal electric field distribution coupled with inhomogeneous strain. We show that high bending strain acts as a probe allowing us to define the electric field distribution with deep subwavelength resolution using the corresponding changes of the Raman spectra.

Photon Drag Currents and Terahertz Generation in α-Sn/Ge Quantum Wells.

We have fabricated α-Sn/Ge quantum well heterostructures by sandwiching nano-films of α-Sn between Ge nanolayers. The samples were grown via e-beam deposition and characterized by Raman spectroscopy, atomic force microscopy, temperature dependence of electrical resistivity and THz time-resolved spectroscopy. We have established the presence of α-Sn phase in the polycrystalline layers together with a high electron mobility μ = 2500 ± 100 cm V s.

Effect of crystal structure on the Young's modulus of GaP nanowires.

Young's modulus of tapered mixed composition (zinc-blende with a high density of twins and wurtzite with a high density of stacking faults) gallium phosphide (GaP) nanowires (NWs) was investigated by atomic force microscopy. Experimental measurements were performed by obtaining bending profiles of as-grown inclined GaP NWs deformed by applying a constant force to a series of NW surface locations at various distances from the NW/substrate interface. Numerical modeling of experimental data on bending profiles was done by applying Euler-Bernoulli beam theory.

Study of local anodic oxidation regimes in MoSe.

Scanning probe microscopy is widely known not only as a well-established research method but also as a set of techniques enabling precise surface modification. One such technique is local anodic oxidation (LAO). In this study, we investigate the LAO of MoSe transferred on an Au/Si substrate, focusing specifically on the dependence of the height and diameter of oxidized dots on the applied voltage and time of exposure at various humidities.

Effect of the Uniaxial Compression on the GaAs Nanowire Solar Cell.

Research regarding ways to increase solar cell efficiency is in high demand. Mechanical deformation of a nanowire (NW) solar cell can improve its efficiency. Here, the effect of uniaxial compression on GaAs nanowire solar cells was studied via conductive atomic force microscopy (C-AFM) supported by numerical simulation.

Direct Growth of Light-Emitting III-V Nanowires on Flexible Plastic Substrates.

Semiconductor nanowires are routinely grown on high-priced crystalline substrates as it is extremely challenging to grow directly on plastics and flexible substrates due to high-temperature requirements and substrate preparation. At the same time, plastic substrates can offer many advantages such as extremely low price, light weight, mechanical flexibility, shock and thermal resistance, and biocompatibility. We explore the direct growth of high-quality III-V nanowires on flexible plastic substrates by metal-organic vapor phase epitaxy (MOVPE).

Control of Conductivity of InGaAs Nanowires by Applied Tension and Surface States.

The electronic properties of semiconductor AIIIBV nanowires (NWs) due to their high surface/volume ratio can be effectively controlled by NW strain and surface electronic states. We study the effect of applied tension on the conductivity of wurtzite InGaAs ( ∼ 0.8) NWs.

Half-disk laser: insight into the internal mode structure of laser resonators.

Usually electromagnetic modes inside a laser resonator are a matter of the theoretical studies. In a sense we manage "to have a look into a whispering gallery mode (WGM) resonator" and observe how the resonator modes arrange in reality. The picture occurs to be quite different from the commonly used Bessel modes in a disk resonator.

Unified mechanism of the surface Fermi level pinning in III-As nanowires.

Fermi level pinning at the oxidized (110) surfaces of III-As nanowires (GaAs, InAs, InGaAs, AlGaAs) is studied. Using scanning gradient Kelvin probe microscopy, we show that the Fermi level at oxidized cleavage surfaces of ternary Al Ga As (0 ≤ x ≤ 0.45) and Ga In As (0 ≤ x ≤ 1) alloys is pinned at the same position of 4.

Young's Modulus of Wurtzite and Zinc Blende InP Nanowires.

The Young's modulus of thin conical InP nanowires with either wurtzite or mixed "zinc blende/wurtzite" structures was measured. It has been shown that the value of Young's modulus obtained for wurtzite InP nanowires (E = 130 ± 30 GPa) was similar to the theoretically predicted value for the wurtzite InP material (E = 120 ± 10 GPa). The Young's modulus of mixed "zinc blende/wurtzite" InP nanowires (E = 65 ± 10 GPa) appeared to be 40% less than the theoretically predicted value for the zinc blende InP material (E = 110 GPa).

Nitride surface passivation of GaAs nanowires: impact on surface state density.

Surface nitridation by hydrazine-sulfide solution, which is known to produce surface passivation of GaAs crystals, was applied to GaAs nanowires (NWs). We studied the effect of nitridation on conductivity and microphotoluminescence (μ-PL) of individual GaAs NWs using conductive atomic force microscopy (CAFM) and confocal luminescent microscopy (CLM), respectively. Nitridation is found to produce an essential increase in the NW conductivity and the μ-PL intensity as well evidence of surface passivation.