High Breakdown Voltage and Low-Current Dispersion in AlGaN/GaN HEMTs With High-Quality AlN Buffer Layer

We have successfully grown AlGaN/GaN high electron mobility transistor (HEMT) structure on the high-quality undoped thick AlN buffer layer with large band offset to replace the conventional high-resistivity GaN buffer layer. The AlGaN/GaN HEMT fabricated on this AlN buffer layer exhibits low off-state leakage current with high Ion/Ioff of ~10⁶ due to enhanced confinement of the electrons in the 2-D electron gas (2-DEG) channel. The undoped AlN buffer layer is responsible for suppressing the trapping effects to greatly reduce the current dispersion in pulsed ID-VD characteristics, which is hardly avoided in conventional deep acceptor-doped GaN buffer layer. The device also demonstrates high breakdown voltage of 2154 V with very high figure of merit (FOM) of ~1.8 GV²⁻¹cm⁻², one of the highest ever reported, suggesting that the AlGaN/GaN-based HEMTs with AlN buffer layer are promising for high-performance RF and power applications.