Ion Implantation Processes in AlN for Wide Bandgap Power Devices

Current and next-generation power systems require power devices that operate at high voltages and high frequencies beyond the reliable operating limit of the present silicon- and silicon carbide- based power devices. The material properties of AlN permit power devices to operate at these extremes, promoting device shrinkage for automotive applications as well as faster switching and more efficient power conversion. The main remaining challenge in wide bandgap semiconductors and in AlN in particular, is effective doping. Our approach will develop ion implantation technology in high-quality AlN for application in the next generation of power devices. In Phase I, we explored the feasibility of ion implantation to incorporate donor and acceptor species that would yield technologically useful carrier concentrations in the high crystalline quality AlN wafers and high-purity epitaxial layers used as a platform for these studies. The extremely low extended defect density and high purity of this material offered the possibility of doping studies without the interference of copious structural defects found in AlN grown on sapphire or SiC and without high concentrations of background impurities that would trap or scatter free carriers. This enabled us to isolate the intrinsic behavior of dopants for the first time and achieve free electron concentration 2 orders of magnitude greater than the highest concentration ever reported in AlN. In Phase II we will expand on our work to develop complete donor and acceptor implantation processes, including high temperature post-implantation annealing procedures for damage recovery and dopant activation that exploit the differences in the kinetic processes involved in defect formation. In addition, other dopant species will be experimentally and theoretically evaluated as possible donors and acceptors. The implantation processes will be expressly developed for use in power electronics by applying them to device technologies that will culminate in the demonstration of an AlN Schottky diode. Achieving the stated objective will enable the manufacture of a new generation of power electronics that enable more efficient electricity conversion. With an ever increasing share of our electricity passing through power conversion devices, the success of this program will directly support the Improved Energy Efficiency mission of DOE and can potentially impact every electrical power consumer in the world.