Influence of the In/Ga relation in the gas phase on the characteristics of the InxGa1-xP epitaxial layers of cascade solar cells

The modern solar arrays for the most spacecrafts consists of solar cells which are formed by the thirty nano- and micro-dimensional epitaxial layers based on AIIIBV materials forming triple junction InGaP / InGaAs / Ge. This article presents the results of a study of experimental samples of thin single-crystal epitaxial InxGa1-xP layers with different indium and gallium concentrations (x = 38 to 53 %) that were grown on Ge - substrate by MOCVD industrial equip- ment. The theme of present investigation is the influence of epitaxial growth parameters on the crystal structure charac- teristics. The ratio of the components of the third group in the gas phase were calculated from the specified technological parameters. The rocking curves obtained by high-resolution two-crystal X-ray diffractometry were investigated. The lattice parameter and the ratio of indium to gallium in the solid phase were calculated. A high perfection of a single- crystal structure with an insignificant broadening of the X-ray diffraction peaks was observed in the range from 45 to 53 %. It is shown that the broadening of the diffraction peak of the structure can be the criterion of estimation of the quality of the grown structure in addition to the mismatch of diffraction maximum. Also the In / (In + Ga) ratio in the solid phase was calculated using the method of photoluminescence effect measuring. It was shown in comparison of data of x-ray diffraction with photoluminescence method the composition determination by photoluminescence method should be considered only as estimated.