X-ray diffraction study of deformation state in InGaN/GaN multilayered structures

High resolution X-ray diffractometry (HRXRD) was used to investigate InxGa₁₋xN/GaN multilayered structures grown by the metal-organic chemical vapor deposition (MOCVD) method. Deformation conditions in the superlattice (SL) and its separate layers, degree of relaxation in the structure layers, as well as the period of the SL, thicknesses of its layers and composition of InxGa₁₋x solid solution in active area were determined. It was found that SL was grown on the relaxed buffer layer. SL layers were grown practically coherent with slight relaxation of InGaN layer (about 1.5 %). The role of dislocations in relaxation processes was established. Analysis of experimental diffraction spectra in these multilayered structures within the frameworks of ParratSperiozu was adapted for hexagonal syngony structures

Formation of ohmic contacts to n(p)-gan and measurement of their contact resistivity

We propose multilayer ohmic contacts to n- and p-GaN layers, with titanium boride as diffusion barrier. It is shown that the optimal method of contact resistivity measurement is the transmission line method (TLM) with circular contact geometry. The Ti−Al−TiBx−Au contact metallization to n-GaN retains its layer structure after thermal annealing at temperatures up to 900 °C. The contact resistivity ρс is (6.69±1.67)×10⁻⁵ Ω⋅cm². For the Au−TiBx−Ni−p-GaN contact structure, the contact resistivity is (1±0.15)×10⁻³ Ω⋅cm²

Deformation state of short-period AlGaN/GaN superlattices at different well-barrier thickness ratios

Dependence of deformation characteristics changing in superlattice (SL) structures AlxGa₁₋xN/GaN with Al (~10%) on the well-barrier thickness ratio in period was studied in this work. The deformation state of SL and individual layers, relaxation level and periods, layers’ thickness and composition of AlxGa₁₋xN layers were analyzed using high-resolution X-ray diffractometry. It was ascertained that the buffer layer and SL layers are compressed in all the investigated structures. Thus, it has been shown that deformation of the SL period depends on the well/barrier thickness ratio. Thicknesses of individual layers in SL strongly depend on the deformation state of the whole system. Increasing the deformation level leads to the increase of the barrier layer thickness