EAGER: A novel route for high activation of implanted p-type regions in vertical Gallium Nitride devices.

Semiconductor based power electronics enabled efficiency improvements could save 1.2 trillion kilowatt-hour by 2030, avoiding approximately 733 million metric tons of CO2. Implementation of wide bandgap materials in power electronic devices is the single most important revolution to further increase system efficiency, reduce the size and weight of devices, improve reliability, and reduce life cycle cost. Among various wide bandgap materials, gallium nitride (GaN) vertical power devices are conceived as a next generation technology. Despite the success of gallium nitride lateral power devices, the implantation of vertical gallium nitride power devices is delayed by limitation of p-n junction and highly doped p layer formation. While n-type junctions via implantation have gained success, p-type junctions formed via implantation are still facing key challenges. Hence, developing an effective highly doped p-type process is a critical need to enable high performance gallium nitride devices. This project aims to address the current challenges of p-type doping on gallium nitride by a novel route for highly doped p-type junctions using the process of solid phase epitaxy. This presents a unique opportunity for achieving high current and high voltage power devices to significantly benefit power electronic systems. The impact of these advances could also drive enhancements in ultra-wide bandgap devices. The proposed novel p-doping can enable wide adoption of vertical gallium nitride power devices and help maintain leadership in wide bandgap semiconductor technology and economic competitiveness. This project provides a hand-on research experience for undergraduate students on device physics, processing, and characterization. The experimental results will be incorporated into undergraduate and graduate courses. This project proposes a novel route for highly doped p-type in gallium nitride using the process of solid phase epitaxy after implantation. This solid phase epitaxy process involves the conversion of a metastable amorphous region containing the targeted p-type dopant into a crystalline region through modest temperature anneals. In prior work on other semiconductors, solid phase epitaxy has shown to result in increased active dopant concentration that is in great excess of the solid solubility limit, decreased damage, reduced channeling, and lower temperature operation. All these characteristics are highly desirable for vertical devices and warrant investigation of solid phase epitaxy in gallium nitride. The proposed process will involve three key steps: a pre-amorphization implantation, a p-type dopant implantation and a moderate temperature anneal to achieve high active concentration. This process is expected to convert the amorphous region containing the targeted p-type dopant into a crystalline region through modest temperature anneals. The recrystallization temperature and time depend on the orientation of the crystalline substrate and the type and concentration of implanted species. The proposed research aims to solve the fundamental problem in III-nitride devices towards high current and high voltage power devices and may also be applied towards emerging ultra-wideband gap materials. The research will be carried out in multiple tasks including molecular dynamic and process simulation, ion implantation, solid phase epitaxy anneal optimization, device fabrication and characterization of structures including transfer line method structures as well as diode structures to assess impact of solid phase epitaxy process on gallium nitride p-junction performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.