Material- and process development of power transistor devices based on β-Ga2O3 with different crystal orientation

• Applicants: Professorin Dr.-Ing. Sibylle Dieckerhoff; Dr. Zbigniew Galazka; Dr. Andreas Popp; Dr.-Ing. Kornelius Tetzner
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Synthesis and Properties of Functional Materials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555506919

The ultra-wide bandgap semiconductor material β-Ga2O3 has drawn a lot of attention in recent years due to expected outstanding material properties making it a promising candidate for next-generation power electronic applications. By taking its very high bandgap of 4.8 eV into account an impressive material breakdown strength of 8 MV/cm is expected which could pave the way for the realization of high voltage switching devices with even higher power densities and efficiencies than it is currently possible using the SiC and GaN counterparts. Recent studies focusing on the development of β-Ga2O3 metal oxide semiconductor field-effect transistors (MOSFETs) have already demonstrated the high potential for high voltage applications showing breakdown voltages up to 8 kV and record average breakdown strength of 5.5 MV/cm for certain devices. However, achieving both i.e. high breakdown voltages and high breakdown fields in the same device has not been achieved yet due to material and device related impairments. Thus, the overall performances of those β-Ga2O3 devices are still far away from the theoretical limit for β-Ga2O3. Moreover, only very few studies on dynamic β-Ga2O3 transistor power switching characterizations have been carried out so far in order to evaluate the actual switching capabilities of this material. In this regard, only 400 V turn-on and turn-off switching transients for β- Ga2O3 MOSFET have been demonstrated up to now. Furthermore, due to the monoclinic structure of β-Ga2O3, substrate and epitaxial layers of various crystal orientations can be fabricated which differ significantly from each other regarding their physical properties and a clear consensus on the optimum surface orientation for lateral power devices hasn’t been reached yet within the scientific community. This proposed project aims for pushing the performance level of current Ga2O3 power MOSFET devices closer to the theoretical limit by optimizing both the material and process technology allowing for reaching high breakdown voltages and breakdown fields in the same device. The targeted specifications of the Ga2O3-based power transistors are set well beyond the current state of the art with maximum currents up to 20 A and breakdown voltages of 1500 V. In order to achieve this goal a unique comparative study of transistor devices fabricated on epitaxial Ga2O3 wafers with different crystal orientations derived from the same crystal boule will be carried out at first. This will ultimately reveal the optimum crystal orientation of Ga2O3 for power MOSFET devices. In a second phase large switching devices will be fabricated for which up to 25x25 mm² epitaxial wafers with the optimum crystal orientation have to be prepared. Static and dynamic characterization of these devices will be carried out along the project as well as device modelling and simulation which is used as a feedback to material and device technology for iterative optimization.

• DFG Programme: Research Grants