Power semiconductor devices are critical for the energy infrastructure. By 2030, as much as 80% of generated electricity will pass through at least one power conversion stage before use. Maximizing the energy efficiency of devices that perform power conversion is therefore of utmost importance. Power switches based on nitrides of Group III elements will be the building blocks of future power grids. While power diodes based on III-nitrides have been developed, research for the next generation of power diodes and switches needs to be initiated. A potential material candidate for the next generation is the ultrawide bandgap aluminum nitride (AlN) and Al-rich aluminum gallium nitride (AlGaN). This project will establish the fundamentals for controlling the electronic properties of III-nitrides by dopant engineering. This provides a robust toolbox for the design of devices based on basic semiconductor processing, but with the understanding that processes need to be tailored to the targeted applications. Doping advances will lead to reliable devices capable of switching unprecedented power densities and operating at temperatures beyond traditional limits. The ultimate impact of this project will be to preserve and extend natural resources by allowing for the efficient use and transmission of electrical energy. This project could also enable the development of ultraviolet LEDs and lasers.
The proposed study will establish advanced doping capabilities in n-type Al-rich AlGaN to realize a doping toolbox as the first step towards the realization of a novel power Schottky diode or HEMT device structure. The program is based on the hypothesis that AlGaN and potentially even AlN can be n-doped with technologically relevant free carrier concentrations to realize the potential expected from such power switches. Based on this hypothesis, the ultimate technical goal is to demonstrate controllable n-type doping in AlGaN, thus realizing a practical doping toolbox to allow for the realization of advanced power device structures. The following challenges need to be met: (1) doping of AlGaN with Si in the low doping range (<10E16/cm^3) for drift layer applications by controlling the compensator background concentration, (2) controlling the free electron concentration in the high doping range (>1E19/cm^3) by identifying and controlling self-compensation, and (3) suppressing DX-center formation by application of non-equilibrium processes such as ion-implantation and quasi defect Fermi level control. In addition, a wider doping range and better compensation control can be achieved by using alternative dopants such as Ge. Our group have been in the forefront of these developments by demonstrating not only novel point defect control schemes but also by demonstrating its capabilities such as the Schottky diode based on AlGaN and deep-UV lasers. The proposed research will develop a unique framework by which to realize the concept of dopant engineering in ultrawide bandgap semiconductors and related electronic materials.
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.
