Vladimir I Kozlovskii

Luminescence of ZnO nanorods grown by chemical vapor deposition on (111) Si substrates

ZnO nanorods have been grown on (111) Si substrates by chemical vapor deposition in a horizontal reactor, with no catalyst. The nanorods grown far from the outlet end of the reactor are larger in size, have a higher structural perfection, and exhibit more efficient room-temperature edge luminescence in comparison with the nanorods grown at the outlet end. The low-temperature cathodoluminescence spectrum of the nanorods also depends on their position in the reactor during growth, which is interpreted in terms of the density of native defects. The nanorods exhibit room-temperature stimulated emission in the excitonic spectral region.

Passive Q-switching of the diode-pumped Er:YAG laser cavity with the Q-switch based on the Fe2+:ZnSe crystal

Repetitive-pulse generation of the diode-pumped Er:YAG laser (λ = 2.94 µm) in the free mode and in the mode of cavity passive Q-switching was achieved using a Q-switch based on the Fe2+:ZnSe crystal. When using pump pulses 3 ms long, the pulse-average output power of the Er:YAG laser in the free generation mode was 0.5W. In the passive Q-switching mode, giant pulses 180 ns long with an energy of 3 µJ were obtained.

Luminescent properties of vertically aligned ZnO nanorod arrays grown on (100) Si substrates

The effect of the dimensions of zinc oxide nanorods on their cathodoluminescence (CL) has been studied in the visible through UV spectral region. The results indicate that hexagonally faceted columnar nanordos grown on (100) Si substrates are aligned almost vertically. The chemistry of point defects in the nanorods is shown to depend on their position in the reactor during growth. The low-temperature CL spectra of the nanorods show peaks due to bound excitons and electron recombination through the nitrogen acceptor level. Electron microscopy results show that the ZnO nanocrystals are highly uniform in shape and size and that these parameters depend on the chemical vapor deposition conditions.

Band offsets in Zn 1−x Cd x Te/ZnTe single-quantum-well structures grown by molecular-beam epitaxy on GaAs(001) substrates

ZnTe heteroepitaxial layers and ZnTe/Zn1−xCdxTe/ZnTe strained quantum-confinement structures grown by molecular-beam epitaxy on GaAs(001) were studied by low-temperature cathodoluminescence spectroscopy and current-relaxation deep-level transient spectroscopy (DLTS). A peak related to electron emission from the ground size-quantization level in the conduction-band was observed in the DLTS spectra of quantum-confinement structures. The conduction-band offset parameter QC was determined from the DLTS and cathodoluminescence data. For Zn1−xCdxTe/ZnTe single-quantum-well structures with x=0.2–0.22, QC equals 0.82 ± 0.05. The effect of internal elastic strain on the band offsets and QC at the CdxZn1−xTe quantum well interfaces was calculated; the results of calculations agree well with experimental data.

Scanning probe microscopy of cleavages of undoped GaInP/AlGaInP and CdS/ZnSSe heterostructures

Cleavages of undoped nanoscale heterostructures with GaInP/AlGaInP and CdS/ZnSSe quantum wells were studied by scanning probe microscopy. A nanorelief formed on the cleavage surface due to elastic stresses in quantum wells was detected by contact methods. The current method yielded more contrast images. It was shown that the current in undoped heterostructures depends on the Schottky barrier on the probe contact with structure layers, the intrinsic carrier concentration in them, the growth substrate doping level, the intensity and spectrum of external illumination.

ZnMgSe/ZnCdSe-based distributed bragg mirrors grown by molecular-beam epitaxy on ZnSe substrates

Molecular-beam epitaxy was used to grow distributed Bragg mirrors on ZnSe substrates. These mirrors are composed of 10.5 and 20 pairs of alternating quarter-wave ZnMgSe and ZnCdSe layers with reflectance peaks at the wavelengths of 530 and 560 nm, respectively, which fall in the transparency region of the substrate. These structures were studied by low-temperature cathodoluminescence, atomic-force microscopy, and transmission electron microscopy. The maximum of the reflection coefficient was 78% for a 20-pair mirror and 66% for a 10.5-pair mirror. This result is interpreted in terms of a model that takes into account the roughness of the interlayer boundaries.

Cathodoluminescence and Raman scattering in Ga1−xAlxP epitaxial films

Low-temperature cathodoluminescence and Raman scattering of Ga1−xAlxP epitaxial layers (0≤x≤0.8) grown by liquid phase epitaxy on the GaP(100) substrate are studied. The obtained cathodoluminescence spectra indicate that the dependence of the indirect energy gap on the composition parameter x is nonlinear. This nonlinearity can be described by the parabolic function with the inflection parameter b=0.13. Raman scattering studies show that the phonon spectrum of Ga1−xAlxP consists of one (Al-P)-like vibrational mode and three (Ga-P)-like modes.

Paramagnetic defects in ZnSe crystals doped with iron ions

The electron paramagnetic resonance (EPR) spectra of iron-doped ZnSe single crystals were studied. In addition to cubic Fe3+ and Mn2+ centers and also Fe2+, and Cr2+ centers, monoclinic Fe3+ complexes locally compensated by Cu+ ions were revealed. Some trigonal centers with a spin of 3/2 were also found and studied. The zero-field splittings of monoclinic centers were measured, and the parameters of the monoclinic and trigonal spin Hamiltonians were determined. The nature of trigonal centers was discussed.

Zinc telluride epilayers and CdZnTe/ZnTe quantum wells grown by molecular-beam epitaxy on GaAs(100) substrates using solid-phase crystallization of an amorphous ZnTe seed layer

The deposition of an amorphous ZnTe seed layer of thickness 10 nm and its subsequent solid-phase crystallization are implemented prior to the start of molecular-beam epitaxy of ZnTe layers on GaAs(100) substrates. RHEED patterns from the growth surface of the samples during epitaxy confirm that the formation of three-dimensional nucleation centers is successfully eliminated by this technique, and two-dimensional growth in the early stage of epitaxy is achieved. Cathodoluminescence and x-ray structural analyses indicate a higher quality on the part of ZnTe layers grown with the application of an amorphous ZnTe layer. Quantum-well ZnCdTe/ZnTe structures that emit efficiently in the green region of the spectrum can be grown by optimizing the epitaxy regimes.

Solid II–VI Solutions as active media for a laser electron-beam-tube

The properties of laser electron-beam-tube (LEBT) laser elements based on solid solutions of II-VI semiconductor compounds are presented. The fundamental absorption edges of these compounds are investigated. Their radiative properties are analyzed. A correlation is found between the emissivities of solid solutions, the characteristics of their fundamental absorption, and the results of investigations of laser elements based on these compounds. It is shown that Zn1−xCdxS and Zn1−xSe are promising solid solutions for use in LEBT operating at T>80 K, while CdS1−xSex and ZnS1−xSex are promising at T<150 K.