High-performance GaN HEMTs with over 2 MV cm ⁻¹ breakdown field and 73% PAE via an AlN super back barrier/ultra-thin GaN channel heterostructure

This work demonstrates a high-performance AlGaN/GaN high-electron-mobility transistor on SiC, featuring an unintentionally doped AlN super back barrier (SBB) and an ultra-thin GaN channel. This structure directly addresses the limitation of conventional Fe- or C-doped buffers, where deep-level dopants induce high trap densities, severe current collapse, and reliability degradation. The AlN SBB/GaN heterointerface provides a large conduction band offset for robust carrier confinement and high intrinsic resistivity for effective leakage suppression. Consequently, the fabricated high-electron-mobility transistors exhibit low off-state leakage, a breakdown field exceeding 2.1 MV cm^-1, and minimal current collapse of only 10.87%. At 3.6 GHz, the device delivers a high output power density of 13.58 W mm^-1at a 70 V drain bias and achieves a peak power-added efficiency of 73.06% at 40 V. These results underscore the effectiveness of the AlN SBB with an ultra-thin channel in simultaneously enabling high breakdown strength, high power, and high efficiency, providing a promising solution for next-generation RF power applications.