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The structures comprising three epitaxial InP layers—buffer (n[sup ++]), active (n), and contact (n[sup +])— were grown by liquid phase epitaxy on porous and compact (control) InP(100) substrates. High quality of the active n-InP layer obtained on a porous substrate (in comparison to the control samples) is confirmed by the values of the halfwidths of the (311) X-ray diffraction reflections (54″ versus 76″), dislocation concentration (5 × 10² - 5 × 10³ cm[sup -2] versus 5 × 10[sup 4] - 5 × 10[sup 5] cm[sup -2]), and electron mobility (4000 cm²/V s versus 30003500 cm²/V s). Using these homoepitaxial InP structures, Au-Ti Schottky diodes with a working mesastructure area of ∼1.8 × 10[sup -6] cm² were prepared. It was found that diodes based on the porous substrates are characterized by significantly smaller leak currents and higher breakdown voltages as compared to those of the control diodes: 1 nA, 27 V versus 200 nA, 15 V. [ABSTRACT FROM AUTHOR]

Lasing is discovered in the direction perpendicular to the surface in quantum-size InGaN/GaN multilayer heterostructures grown by vapor-phase epitaxy. At high excitation densities one of the modes in the luminescence spectrum, which is modulated by modes of the Fabry-Pérot cavity formed by the GaN/air and GaN/sapphire-substrate interfaces, is sharply amplified and begins to dominate the spectrum. The dependence of the luminescence intensity on pump density has a clearly expressed threshold character. The threshold excitation density in the vertical direction is 5-6 times greater than the stimulated-emission threshold for observation from an end surface of the structure. The gain coefficient in the active region at the threshold for surface-emitting lasing is estimated as 2 × 10[sup 5] cm[sup -1]. The interaction between the cavity modes and the gain spectrum is detected in the form of displacement (by up to 2.6 nm) of modes on the short-wavelength edge of the luminescence spectrum toward higher photon energies. The characteristic temperature (T[sub 0]) measured in the range from 16 to 120 K is 480 K. At higher temperatures T[sub 0] = 70 K. [ABSTRACT FROM AUTHOR]

The films of amorphous hydrogenated carbon containing cobalt nanoparticles are studied by small-angle X-ray scattering (SAXS). The SAXS pattern structure reveals the presence of two types of scattering centers, one of which represents cobalt particles. It is suggested that the second type of scattering centers can represent the groups of nanoparticles possessing a localized electron wavefunction and forming a cluster electron state. [ABSTRACT FROM AUTHOR]

Multi-technique structural and electro-physical investigations of VO[sub 2] films on SiO[sub 2]/Si substrates are carried out to study the microscopic nature of fluctuator defects — sources of low-frequency flicker noise. It is established that the noise intensity is determined by the magnitude of the microstress fluctuations 〈ε〉={〈(δc/c)[sup 2]〉}, where c is the lattice parameter along the c-axis parallel to [011] direction in the blocks of which the film is formed. The dimensions of the blocks were determined in the direction of the c-axis (t[sub c]∼1000 Å). The suggestion is put forward that the samples contain two types of fluctuator defects: 1) V atoms jumping between the two nearest interstitial sites and 2) V atoms jumping between these interstitial sites near lattice defects. [ABSTRACT FROM AUTHOR]