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In this work, the influence of the Fe and Fe/C co-doped buffer on the AlGaN/GaN HEMTs is systematically investigated and compared. Due to the pronounced Fe tail in the unintentionally doped layer of the Fe-doped buffer compared to the Fe/C co-doped buffer, and the utilization of a two-step C doping process in the Fe/C co-doped buffer, it results in effectively reducing leakage current and increasing breakdown voltage without sacrificing saturation current and peak transconductance. Meanwhile, the RF characteristics of the Fe/C co-doped buffer are also superior to the Fe-doped buffer. More importantly, Drain Transient Current measurements indicate that the current collapse in the Fe/C co-doped buffer is smaller than that in the Fe-doped buffer. Through simulation analysis, the reason was identified: In the near-channel region, the weaker Fe tail effect in Fe/C co-doped buffer leads to a lower acceptor trap ionization. When the concentration of C exceeds 1 × 1016 cm−3, the ionization of traps introduced by Fe is suppressed. Additionally, the two-step C impurity distribution in the Fe/C co-doped buffer design modulates the electric field and potential, reducing the effective range of the electric field and potential, thereby effectively reducing the trap effects. These results are highly meaningful for the design of high-power amplifier epitaxial structures. [ABSTRACT FROM AUTHOR]

To improve the threshold voltage and gate reliability of conventional enhancement-mode p-GaN-gated AlGaN/GaN high electron mobility transistors while maintaining a low on-resistance, an improved design solution for p-GaN HEMTs with P-I-N junction gate (PIN-HEMTs) has been proposed. Simulation results show that energy band modulation is achieved by adjusting the doping concentration and thickness of each layer of the PIN junction, and high-performance p-GaN gate HEMTs with adjustable threshold voltages ranging from 0.56 V to 4.75 V and gate breakdown voltages ranging from 19.8 V to 30.3 V would be prepared. The PIN-HEMT has a quasi-self-alignment property, which means that good gate control is independent of gate metal alignment. This not only improves the production efficiency but also solves the problems of weak gate control and electric field aggregation at the gate edge caused by the gate misalignment in conventional p-GaN gate HEMTs, thus realizing lower on-resistance and higher gate breakdown voltage, which demonstrates this proposed structure has excellent potentials for realizing effective and reliable high-power transistors. [ABSTRACT FROM AUTHOR]

In order to achieve high‐performance gallium nitride (GaN) high‐electron‐mobility‐transistors (HEMTs) capable of operating in the X‐band, a bilayer passivation technique is employed. The technique involves creating a stacked passivation layer consisting of a 20‐nm Si‐rich silicon nitride (SixN) passivation layer and a 100‐nm N‐rich silicon nitride (Si3N4) passivation layer. This effectively reduces radio frequency scattering in GaN HEMTs without compromising the breakdown voltage (BV). On the one hand, the SixN passivation layer effectively suppresses the surface states of devices, resulting in low current collapse. On the other hand, the Si3N4 passivation layer can effectively reduce gate leakage caused by the SixN passivation layer, allowing the device to reliably operate at higher voltages. Consequently, a GaN HEMTs with SixN/Si3N4 bilayer passivation achieve a low current collapse of 5% and a high BV of 157 V. The device features a current gain cutoff frequency (fT) and maximum oscillation frequency (fmax) of 57.9 and 96.8 GHz, respectively. Additionally, it exhibits excellent radio frequency performance in the X‐band, with an output power density (Pout) of 13.7 W mm−1 and power added efficiency of 60.8% at a drain voltage (VD) bias of 50 V. [ABSTRACT FROM AUTHOR]