Seminar series - Field effect transistors based on III-nitride heterostructures for power switching applications
3. 5. 2023, 14:00 - 15:30
CEITEC BUT, large meeting room, S building
Assoc. Prof. Dionyz POGANY
Due to wide energy band gap, heterostructure tunability and excellent transport properties, III-nitride semiconductors are used in many opto-electronic, RF and power switching applications. For the latter, including green energy solutions, field effect transistors (FETs) with a high breakdown voltage, current driving capability and reliability are desirable. I start my talk with introducing AlGaN/GaN heterostructure system and “polarization-doping” concept used to form a two-dimensional electron gas FET channel. I will present FET designs for normally-on and normally-off operation, the latter concept being preferable for power applications. Although power FETs on GaN/Si-substrate plattform outperform leading silicon devices in some applications, there are still performance and reliability issues which limit reaching theoretical expectations of GaN material. These are parasitic effects related to high density of point and extended defects, the latter being due to lattice mismatch between III-nitride buffer and Si substrate. I will briefly discuss (i) dynamic on-resistance due to trapping to buffer and surface states [1,2], (ii) threshold voltage instability in GaN FETs with dielectrically isolated gate due to lack of suitable interface state passivation [3-5], (iii) lack of avalanche breakdown in lateral FETs due to dominance of defect-related breakdown mechanisms.