AlGaN/GaN microwave transistors for wireless communication systems and advanced nanostructures for high-speed sensor applications

We presented a systematic study of the impact of a layer structure design on the performance of AlGaN/GaN high electron mobility transistor structures. The new mechanism of strain relaxation by twisted nanocolumns was revealed. The experimentally obtained results were found to be in good agreement with the proposed model. Device layer structures were optimized to obtain a minimum overheating temperature at high dissipated power in HEMT channels. It was shown that the room-temperature spectra can be used to determine the activation energy of the traps. In addition, the impact of layer structure design on the properties of the 1/f flicker noise was studied and the phase noise performance of test microwave HEMT-based oscillators was discussed. The noise and capacitance spectroscopy of double-barrier RTDs were found to be a powerful and sensitive tool for the exploration of transport features and structural quality. The results can be used to design AIN/GaN RTD-FETs with optimized layout, to conduct a more efficient analysis of resonant tunneling processes, and to improve the peak-to-valley ratio of NDR regions.