Engineering of Interface Barrier in Hybrid MXene/GaN Heterostructures for Schottky Diode Applications.

The Fermi level position at the interface of a heterostructure is a critical factor for device functionality, strongly influenced by surface-related phenomena. In this study, contactless electroreflectance (CER) was utilized for the first time to investigate the built-in electric field in MXene/GaN structures with the goal of understanding the carrier transfer across the MXene/GaN interface. Five MXenes with high work functions were examined: CrC, MoC, VC, VC, and TiC.

Novel type of whisker-tip cantilever based on GaN microrods for atomic force microscopy.

High-resolution scanning probe microscopy (SPM) is a fundamental and efficient technology for surface characterization of modern materials at the subnanometre scale. The bottleneck of SPM is the probe and scanning tip. Materials with stable electrical, thermal, and mechanical properties for high-aspect-ratio (AR) tips are continuously being developed to improve their accuracy.

Role of Temperature in Arsenic-Induced Antisurfactant Growth of GaN Microrods.

Due to the antisurfactant properties of arsenic atoms, the self-induced dodecagonal GaN microrods can be grown by molecular beam epitaxy (MBE) in Ga-rich conditions. Since temperature is a key parameter in MBE growth, the role of temperature in the growth of GaN microrods is investigated. The optimal growth temperature window for the formation of GaN microrods is observed to be between 760 and 800 °C.

Observation of a hybrid state of Tamm plasmons and microcavity exciton polaritons.

We present evidence for the existence of a hybrid state of Tamm plasmons and microcavity exciton polaritons in a II-VI material based microcavity sample covered with an Ag metal layer. The bare cavity mode shows a characteristic anticrossing with the Tamm-plasmon mode, when microreflectivity measurements are performed for different detunings between the Tamm plasmon and the cavity mode. When the Tamm-plasmon mode is in resonance with the cavity polariton four hybrid eigenstates are observed due to the coupling of the cavity-photon mode, the Tamm-plasmon mode, and the heavy- and light-hole excitons.

Exciton-polariton gas as a nonequilibrium coolant.

Using angle-resolved Raman spectroscopy, we show that a resonantly excited ground-state exciton-polariton fluid behaves like a nonequilibrium coolant for its host solid-state semiconductor microcavity. With this optical technique, we obtain a detailed measurement of the thermal fluxes generated by the pumped polaritons. We thus find a maximum cooling power for a cryostat temperature of 50 K and below where optical cooling is usually suppressed, and we identify the participation of an ultrafast cooling mechanism.

Inhibition and enhancement of the spontaneous emission of quantum dots in micropillar cavities with radial-distributed Bragg reflectors.

We present a micropillar cavity where nondesired radial emission is inhibited. The photonic confinement in such a structure is improved by implementation of an additional concentric radial-distributed Bragg reflector. Such a reflector increases the reflectivity in all directions perpendicular to the micropillar axis from a typical value of 15-31% to above 98%.

Influence of static atomic displacements on composition quantification of AlGaN/GaN heterostructures from HAADF-STEM images.

In an earlier publication Rosenauer et al. introduced a method for determination of composition in AlGaN/GaN heterostructures from high-angle annular dark field (HAADF) images. Static atomic displacements (SADs) were neglected during simulation of reference data because of the similar covalent radii of Al and Ga.

Composition mapping in InGaN by scanning transmission electron microscopy.

We suggest a method for chemical mapping that is based on scanning transmission electron microscopy (STEM) imaging with a high-angle annular dark field (HAADF) detector. The analysis method uses a comparison of intensity normalized with respect to the incident electron beam with intensity calculated employing the frozen lattice approximation. This procedure is validated with an In(0.

Monolithic ZnTe-based pillar microcavities containing CdTe quantum dots.

Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used.