Analysis of High Electron Mobility Transistors for 5G communications, based on GaN with different epitaxial substrates

The purpose of this thesis is to present and discuss the results of a thermal characterization and a deep-level analysis carried out on some High-Electron-Mobility Transistors (HEMTs) for radio-frequency applications. The studied devices implement different technological solutions, aimed at mitigating the impact of the typical short-channel effects, and others non-idealities. In particular, are reported the results on devices based on: (1) doped buffer, (2) back-barrier confinement, and (3) QuanFINE® confinement technology. During the first phase, the temperature dependence of the static parameters was evaluated through a set of DC characterizations at different thermal, and bias conditions. These tests aim to investigate the variations of the main static parameters, correlating them to the different epitaxy, while comparing the observed behavior with the literature. In particular it was attempted to correlate the threshold voltage VTH shift with a change in the Schottky barrier height. Moreover, the obtained results show a stronger VTH shift in the QuanFINE® confinement devices, shift not explainable with a variation of the effective Schottky barrier height. For this reason, in the second part of the activity, drain-current-transient (DCT) and VTH transient measurements were adopted to study the dynamic behavior of this subset of the devices. These measurements aim to investigate the impact of the traps dynamic to the devices’ performance, proving a correlation between the thermal behavior and the observed traps dynamics.