Safriuk N. Х-Ray characterization of multilayered systems Al(In)GaN on polar planes of sapphire.

The thesis deals with investigation of relaxation processes for multilayered systems Al(In)GaN grown on polar planes of sapphire, using complex of theoretical and experimental approaches. The new mechanism of strain deformations relaxation for multilayer structures AlGaN/GaN/Al2O3(0001), that connected with different angles of twisted of GaN unit cells with respect to c-axis of sapphire depending on substrate thickness was established. The influence of template type on structure quality of superlattices (SL) AlN/GaN was established. It was found that for SL grown on AlN-templates the relaxation of strains occurs through formation of dislocations, while for structures on GaN-template they relaxed through cracking process. We explain these effects by influence of residual strains in system template/buffer. The effect of thinning of quantum wells (QW) GaN and respectively thickening of barriers AlN was shown to be much strong for structures grown on strained AlN-template than on fully relaxed GaN-template. Виявлено вплив кількості квантових ям в НГ InxGa1-xN/GaN на співвідношення товщин яма/бар'єр і вміст індію в квантових ямах. For MQW systems InxGa1-xN/GaN grown by MOCVD was found the correlation between deformation state, thickness ratio of wells/barriers, indium content within QW and quantity of QW.