New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.     

Calculation of a quasi-stationary field in the layered medium

A method of calculating the field of a single point charge in a layered medium is suggested. The method makes it possible to simplify the computational formulas for the potential. The solution of the problem employs the properties of Bessel and Struve functions. The results apply to a wide class of problems solvable in terms of Green’s function.     

Stabilization of the melt composition in Ga?Al?Sb?As

In this work we present a new effect of stabilization of the Ga Al Sb As melt composition when it is in contact with the GaAs substrate. It was found that the As content in the Ga Al Sb As melt did not depend on the initial Sb concentration when the liquid phase was formed by saturating the Ga Al Sb melt from the GaAs substrate. This effect is supposed to be due to the change in phase equilibria conditions caused by large lattice mismatch between the substrate and the solid in equilibrium with the liquid.     

The influence of lattice mismatch upon defects generation and luminescent characteristics of heterostructures in the GaP-InP system

The influence of lattice mismatch and thermal stresses on the defect generation in GaAs-GaInP heterostructures was studied. The results of electron-probe, X-ray topographic and electron-microscopic investigations are presented. The comparison of X-ray diffraction and microcathodoluminescence results is done.     

Determination of the Thicknesses and Visualization of Ion-Exchange Waveguides in Glasses by Scanning Electron Microscopy

Technical Physics - The formation of a surface layer with silver and sodium concentration gradients in K8-grade glasses as a result of ion exchange is demonstrated by scanning electron microscopy...     

GaAs quantum well structures investigation by local cathodoluminescence

The article shows the cathodoluminescence technique application to a quality analysis of a semiconductor multilayer heterostructures. Two structures with a GaAs quantum well embedded between the AlGaAs and GaInP barriers were investigated. The AlGaAs/GaAs/GaInP and GaInP/GaAs/AlGaAs structures were grown by MOCVD on a GaAs substrate. In this work we study the interface quality of quantum-dimensional GaAs layer by means of the local cathodoluminescence. Degradation and broadening of GaAs/GaInP interface occurring during the growth process of GaAs on GaInP layer was assumed to result in the formation of a layer with mixed composition at the interface. In addition, the presence of the layer prevented the formation of a quantum well in the GaAs layer. The transition layer was clearly observed by the cathodoluminescence. In the other case it was found that the growth of a structure with GaAs layer on top of AlGaAs produced a quantum well with a 10 nm thickness. The interface quality and layer thicknesses were also confirmed by the X-ray diffraction investigation of these structures.     

The study of the influence of deep level defects on GaAs epilayer electrophysical parameters with electron beam and photoelectron paramagnetic resonance methods

Deep level point defects in the GaAs p⁺-p^ˆ−n^ˆ structures, grown by liquid-phase epitaxy, were investigated with electron-beam methods (electron-beam induced current and modulation method) and photo-EPR. It was shown that during the growing process the donor As_Ga antisite defects with levels ev + 0.52 eV and ec — 0,75 eV and acceptor defect with the level ev + 0.44 eV have appeared. The interconnection between the thickness of p^ˆ-layer, the concentration of deep levels defects, diffusion length of the minority carriers in the p° and n°-layers was found.     

Energy band-gap in elastic-strained heteroepitaxial layers

The effect of internal elastic stress on energy band-gap shift in the A³B⁵ heteroepitaxial layers was investigated. The possibilities to get higher accuracy of divergent beam X-ray stress determination method, designed in the scanning electron microscope (SEM), was presented. X-ray topography method in the SEM with X-ray magnification from 2 up to 10 was for the first time described. The epilayer photoluminescence (PL) peak energy shift as a function of internal elastic stress was measured on the GaInP/GaAs, GAInAsP/InP heterostructures and the influence of different factors on the accuracy of the results was discussed.