ScAlN-based HEMTs: Challenges and opportunities

The rapid advancement of wireless communication, radar technology, automotive electronics, and renewable energy systems necessitates semiconductor devices capable of operating at increasingly higher frequencies and power densities while maintaining reliability. GaN-based high-electron mobility transistors (HEMTs) have demonstrated superior power density, breakdown voltage, and operational frequency, compared to silicon-based devices. However, challenges related to thermal stability, efficiency, reliability, and scalability persist. Scandium-alloyed aluminum nitride (ScAlN) has emerged as a promising alternative barrier material, owing to its significantly enhanced spontaneous and piezoelectric polarization, which leads to increased two-dimensional electron gas density at the heterointerface. In addition to its exceptional thermal stability, ScAlN supports favorable electron mobility despite the high polarization, offering a technically viable balance between charge confinement and carrier transport. These attributes position ScAlN/GaN HEMTs as strong candidates for next-generation high-power and high-frequency applications, including 6G communications, space electronics, and quantum computing. This review provides comprehensive analysis of ScAlN-based HEMTs, encompassing their fundamental material properties, epitaxial growth methodologies, and device performance metrics. Furthermore, we examine the advantages of ScAlN in enhancing device characteristics while addressing key challenges related to epitaxial growth, interface defects, and integration with existing fabrication processes. By overcoming these technological barriers, ScAlN-based HEMTs have the potential to revolutionize high-power electronics and enable the next generation of semiconductor technologies.