Ph.D Thesis

Ph.D StudentKatz Oded
SubjectNitride Based Heterostructure Field-Effect Transistors
for High-Frequency and High-Power Applications
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROFESSOR EMERITUS Gad Bahir


Group III-nitride based heterostructure field-effect-transistors (HFET) show great advantages for high power microwave applications. The advantages of the GaN material system over the conventional III-V compounds include a larger band-gap, a larger breakdown electric field, a larger conduction band discontinuity, and the presence of large polarization field that induces a high two-dimensional electron gas concentration.

In this study, we have focused on these main phenomenological and physical issues such as, the origin of device instabilities (i.e. persistent effects), and the low frequency noise. We have presented a general model that describes the persistent temporal evolution for barrier-controlled devices.  We have showed that from the same model can produce 1/f noise spectra, using Lengenvin method.

The AlGaN/GaN heterostructure formed a new class of two-dimensional systems, in that a large concentration of electrons can be induced without doping, as a result of spontaneous and piezoelectric polarization. We have dealt with the special transport properties of polarization induced two-dimensional electron gas in AlGaN/GaN HFET channel. As a result of the large carrier concentration, we have also developed a general description of extracting mobility and analyzing transfer characteristics in the case of FET with highly non-linear mobility.

Finally, we have presented a novel nitride-based HFET with InAlN/GaN heterostructure, which was demonstrated for the first time as part of this study. This work shows that the InAlN/GaN HFET holds great advantages, and may solve some of the performance limiting properties of the more conventional AlGaN/GaN HFET.