Recently much attention gained development of “buffer free” AlGaN/GaN HEMT structures with thin high quality AlN nucleation layer for better carrier confinement in the transistor channel mitigating short channel effects and with reduced thermal resistance. In this work results of development of low resistivity Ti/Al/TiN/Au ohmic contacts to such a structures will be presented . The impact of annealing temperature and different metal layer thickness on the ohmic contact formation, morphology and structural and electrical properties was studied. Low contact resistance of 0.28 Ωmm was obtained for metal stack with Ti/Al 20nm/80nm thickness after annealing at 750°C. Developed ohmic contacts were integrated in the AlGaN/GaN HEMT fabrication process. Good electrical characteristics were obtained showing high on-state current up to 0.95 A/mm. These prove applicability of developed process in technology of buffer-free AlGaN/GaN high electron mobility transistors.
The aim of the study was to elucidate influence parameters of magnetron sputtering process on growth rate and quality of titanium dioxide thin films. TiO2 films were produced on two inch silicon wafers by means of magnetron sputtering method. Characterization of samples was performed using ellipsometer and atomic force microscope (AFM). Currentvoltage (I-V) and capacitance-voltage (C-V) measurements were also carried out. The results enable to determine impact of pressure, power, gases flow and process duration on the physical parameters obtained layers such as electrical permittivity, flat band voltage and surface topography. Experiments were designed according to orthogonal array Taguchi method. Respective trends impact were plotted.
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