Addressing Challenges in AlGaN-Channel High Electron Mobility Transistors

Next-generation semiconductor switches and integrated circuits require higher power density, greater customizability, and improved radiation hardness than what is commercially available today. Nitride-based Ultrawide-Bandgap (UWBG) semiconductors, namely AlGaN (aluminum gallium nitride) are well-suited to meet these performance demands. Higher bandgaps result in exponentially higher critical electric fields, thus enabling power electronics with larger breakdown voltage and output power than devices made from conventional semiconductors (e.g., Si, GaN). In elevated temperatures, large bandgaps reduce noise and leakage from intrinsic carrier effects and thermionic emission. However, AlGaN faces challenges in realizing low-resistance Ohmic contacts and reduced mobility due to alloy scattering.<br/>This talk will discuss efforts at Sandia to address these challenges, as well as highlight key device results.<br/>Significant improvements of Ohmic contacts on aluminum rich HEMTs (channel compositions of Al_0.7Ga_0.3N) have resulted in reduced specific contact resistance values, with latest developments reaching the 10^-6 Ωcm² range. The power transistor developments have targeted increases in current and standoff voltage, while processes to realize p-AlGaN based enhancement mode (normally off) gates have been developed.<br/><br/><i>SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. Research was sponsored by the Army Research Office and was accomplished under Cooperative Agreement Number W911NF-22-2-0163. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.</i>