Development of high-performance gan-based power transistors.

摘要

This thesis presents a comprehensive study on the development of GaN-based high-power transistors. First, selective area growth by plasma-assisted molecular beam epitaxy, a technology developed by our group for Ohmic contact improvement, is utilized to fabricate large-periphery AlGaN / GaN high electron mobility transistors (HEMTs) for high current operation. A novel Ti / Al multi-layered contact scheme is then introduced to further reduce the contact resistance by inhibiting the Al diffusion during Ohmic contact annealing. Second, to reduce the gate leakage current and enhance the breakdown voltage, gate-SiO 2 deposited by radiofrequency magnetron sputtering is investigated. The routinely occurring degradation of the two-dimensional electron gas properties due to the sputtering-induced surface damage is effectively removed by a buffer layer protection or a post-annealing treatment. A metal-oxide-semiconductor (MOS)-HEMT with sputtered-gate-SiO2 is demonstrated for the first time, which exhibits a record high breakdown voltage density. Furthermore, the sputtered-SiO2, together with the atomic-layer-deposited-Al 2O3, forms a bimodal-gate-oxide scheme, which is combined with the fluoride-plasma treatment to realize high-performance enhancement-mode MOSHEMT. Finally, a new transfer printing approach is developed to fabricate flexible hybrid inductorcapacitor (LC) filters via the pre-etched silicon-on-insulator wafer. The selectively patterned semi-stable Si-supporting membranes are sufficiently robust to support the entire device fabrication process, yet flexible enough to facilitate the subsequent transfer printing via adhesive stamp. The flexible hybrid LC filter has the potential to be incorporated into GaN-MOSHEMTbased high power DC-DC converters.