Abstract <p>This study analyses a gallium nitride (GaN) high electron mobility transistor (HEMT) featuring a&#xa0;double-deck gate field plate (FP) structure to achieve enhanced performance metrics by integrating dual and triple-material barrier configurations. The proposed structure is evaluated using aluminum gallium nitride (AlGaN), indium aluminum nitride (InAlN), and indium aluminum gallium nitride (InAlGaN) as barrier materials in symmetric and asymmetric configurations. The results indicate that AlGaN, when used as a barrier material, offers a higher breakdown voltage (<i>V</i>_Br) than InAlN and InAlGaN. Conversely, although InAlN and InAlGaN exhibit lower breakdown voltages, they demonstrate significantly higher drain saturation currents (<i>I</i>_dss) than AlGaN. The objective of this research is to develop a structure capable of achieving both high <i>V</i>_Br and <i>I</i>_dss. To this end, dual and triple-material barrier configurations were evaluated within a&#xa0;single device structure. The analysis of dual-material barrier structures revealed that the symmetric Case III (AlGaN+InAlN) configuration with 17 nm barrier thickness provided the most favourable results, yielding a&#xa0;<i>V</i>_Br of 404 V and an <i>I</i>_dss of 2.34 A/mm. When comparing traditional AlGaN/GaN, InAlN/GaN, and InAlGaN/GaN HEMT structures to those incorporating triple symmetric barrier materials, it was observed that the symmetric Case F (InAlGaN+InAlN+AlGaN) configuration, with a thickness of 17 nm, achieved the highest <i>I</i>_dss value of 2.96 A/mm. This same configuration also produced the highest <i>V</i>_Br of 569 V, which, while higher than that of InAlN and InAlGaN, was still lower than that of AlGaN. Overall, the results demonstrate that the triple-barrier structure (Case F, 17 nm) outperforms the dual-material barrier structure (Case III, 17 nm) in terms of both breakdown voltage and drain saturation current.</p>