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.     

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...     

Calculation of the Green function for the Laplace equation

A modification of the traditional method of calculating the Green function in a layered medium is suggested that allows one to substantially increase its accuracy. In addition, a technique for calculating the Green function that makes it possible to control the accuracy of the calculated potential is offered. This technique is based on the properties of the Bessel and Struve functions. An example of calculation using the suggested technique is illustrated. The results may be extended for a wide class of problems the solution to which requires calculation of the Green function for the Laplace equation in a layered medium.     

Investigation of multiple layer heterojunction structures by means of an electron-beam microprobe-analyzer

Multiple layer heterojunction structures in the AlAs GaAs system are investigated by means of an X-ray microanalyzer. The quantitative determination of Ga and Al is extensively discussed. The correction for atomic number, absorption and secondary fluorescence are considered. For Al_xGa_1–xAs layers it is favourable for quantitative analysis the AlK_α-emission for x < 0,3 and the GaK_α-emission for x > 0.3. Some multilayer heterojunction structures of laser and luminescence diodes are shown in form of their AlK_α microprobe diagrams.     

Liquid phase epitaxy of AlxGa1–xAs-GaAs heterostructures

This paper is concerned with the investigation of the peculiarities of the application of liquid phase epitaxy for obtaining multilayer structures with heterojunctions in the AlAs–GaAs system. Segregational depletion of Al in liquid and in solid phases is characteristic of this system. It is proved that supercooling of the substrate and numerous inclusions of Al allow to decrease this segregational depletion of Al and to obtain layers of nearly constant composition up to 600 μm in thickness. A new technique of crystallization of structures from a limited volume of melt with the change of solutions by way of compulsory squeezing out of the foregoing solution by the following one is put forward with the view to perfect the planarity of multilayer structures with abrupt heterojunctions and to improve the complete change of solutions on a substrate. The results of the study of various methods of controlling the value and direction of the Al concentration gradient are listed. It has been proved that structures with fluent increase of Al concentration during the crystallization process and also structures with alteration in the gradient direction of Al concentration may be obtained by way of artificial slowing down or acceleration of the process of mixing up solutions of various compositions.