Akademik Veri Yönetim Sistemi
Gazi University Journal of Science Part A: Engineering and Innovation, cilt.12, sa.4, ss.1013-1027, 2025 (ESCI, TRDizin)
It is well known that a fast response is a crucial property of crystal structures used in the design of optoelectronic devices. In line with this, the study investigates an AlxGa1-xN high electron mobility transistor (HEMT) grown on double-polished sapphire using the metal-organic chemical vapor deposition (MOCVD) technique. These structures are durable to high temperature, pressure and voltage. Sapphire (Al2O3) is the most common wafer in growth of group-III nitrites. Graded AlGaN is one of the layers grown. Here Al ratio is at a determined Δx range. Other layer is in standart HEMT structure. Crystallite size and lattice strain are determined by using Williamson-Hall (W-H) method dependent on X-ray peak broadening analysis. Also, other physical parameters such as energy density, stress and strain, are obtained by using different models dependent on W-H method. These models are, Uniform deformation model (UDM), Uniform deformation stress model (UDSM) and Uniform deformation energy density model (UDEDM). In accordance with these models, lattice broadening and relaxation are seen in graded AlGaN buffer layer. Crystallite size is formed by tiny particles. Grain size of graded layer is increasing and micro-strains shift to small values. From this point of view, it is understood that graded buffer layer makes differences in deformation properties. Strain value of graded AlGaN value is shifted from 2.1x10-3 to 1.05x10-3. For this reason HEMT structure should be optimised. Additionally, the spectral vibrations of the sapphire, GaN, and AlN layers were characterized using Raman spectroscopy.