WP1
The major issue of GaN-on-Si is the lack of understanding of the impact of the high defect density on the long term performance. In this project we obtained insights on new mechanisms that determine this behavior, published in several high-impact publications. Buffer structures with improved performance were demonstrated. Novel HEMT configurations were optimized, achieving low sheet resistance far below 300 Ohm/sq.
AlN on sapphire templates with very high quality were fabricated. These served as the substrate for the epitaxy of extreme wide bandgap HEMT structures. Transistors fabricated out of this material show a critical electrical breakdown strength well above the capabilities of GaN material.
WP2
Optimization of state-of-the-art gold-free Ti-Al-based ohmic contacts resulted in a significant yield improvement on AlGaN HEMT technology from the foundry ON-Semiconductor. The normally-off transistors developed by ON-Semiconductor showed high yield > 83% on all critical parameters assessed on large power bars (70 mm). Activities on advanced architectures based on substrate removal and AlN backside deposition (LSR) have been successfully achieved. Finally, a novel AlN-based HEMT technology with functional transistors having low leakage current, remarkable breakdown voltage and high temperature stability have been achieved.
WP3
Yield and reliability are the two key factors to initiate and accelerate market adoption of new/emerging technologies. During the second half of the project ON Semiconductor’s primary focus was to develop reliable eGaN devices using a p-type doped gate architecture. Several epitaxial, process and device architecture development were carried out resulting in manufacturing of eGaN power devices, which met all reliability (dynamic RDS,on, ohmic contacts, pGaN gate and buffer) and Safe Operating Area (Power-to-Failure area higher than hard-switching operating regime area) requirements. Furthermore, a Baseline activity was performed in order to evaluate the stability of the eGaN process resulting in >80% yield figure considering over several Lots/Wafers.
WP4
Within three varieties of planar half-bridge designs (Siemens demonstrator, Bosch verification and technology demonstrator) and a non-isolated DC2AC converter the increased performance of such low-inductive module designs with GaN HEMTs inside could be approved. The assigned advantages of these next generation III-V compound devices - e.g. steeper switching gradients and faster switching capability, lower power consumption in the control circuitry, and derivable from those higher power densities and higher efficiencies - were confirmed by wide band gap adjusted hardware design and realization, and attending functional measurements.
Basing on those attained results from module design and functionality, a subsequent generation of devices close to an engineering grade that represents one-step before industrialization could be possible.
