Emerging applications including advanced industrial manufacturing, cutting-edge scientific research and medical equipment demand AlGaN/GaN HEMTs possessing both high-frequency and high-voltage characteristics. However, a persistent trade-off remains between the frequency characteristics and breakdown characteristics of these devices. In this study, we employed localized electric field tailoring (LEFT) by introducing materials with different dielectric constants to construct a non-uniform composite gate dielectric layer, aiming to balance the breakdown voltage and cut-off frequency of the device. Device models were developed using APSYS-2018 software and their reliability was experimentally validated. Research data indicates that, compared to traditional uniform high-k (typically with dielectric constants k > 10, such as HfO₂ and HfZrO) gate dielectrics, the non-uniform composite gate dielectric structure demonstrates superior transconductance, saturation current density and cut-off frequency, with minimal degradation in breakdown voltage. Specifically, relative to HfO₂ and HfZrO uniform devices, the Al₂O₃/HfO₂ and Al₂O₃/HfZrO non-uniform HEMTs achieved 20.0% and 35.2% increases in cut-off frequency, respectively. Meanwhile, breakdown voltage remained above 97% of their uniform counterparts, saturation current density and transconductance increased by approximately 5%. Therefore, this non-uniform composite gate dielectric layer structure of AlGaN/GaN HEMT with LEFT holds great potential for industrial plasma generators, magnetic resonance imaging systems and biomedical radiofrequency hyperthermia devices.

Gallium nitride semiconductors are essential for advanced electronics, but realizing their potential requires robust normally-off devices. The P-GaN gate high-electron-mobility transistor is the dominant architecture, yet its threshold voltage is restricted to less than 2 volts by the low activation efficiency of magnesium acceptors. Here, we demonstrate atomically confined insertion to overcome this bottleneck. This technique creates self-terminating, two-dimensional magnesium layers within a complex heterostructure, inducing localized strain and polarity inversion. The resulting atomic-scale polarization fields increase the average effective hole concentration several-fold. When integrated into a P-GaN gate high-electron-mobility transistor, atomically confined insertion boosts the threshold voltage from 1.5 to 4.3 volts while mitigating the degradation in transconductance and output current typical of conventional methods. Furthermore, this approach substantially suppresses the current collapse effect via an efficient vertical hole injection mechanism. This work establishes atomic-scale field engineering as a viable axis for performance control and optimization in semiconductor devices.