Modulating the Gas Sensing Performance of GaN Monolayer Toward SF ₆ Decomposition Products via Transition Metal Doping

In gas‐insulated equipment, detecting trace sulfur hexafluoride (SF6) decomposition products is critical for diagnosing insulation faults. Here, the thermodynamic stability, gas adsorption behaviors toward key SF ₆ byproducts (H ₂ S, SO ₂ , SOF ₂ , and SO ₂ F ₂ ), and the electronic transport properties of transition‐metal‐doped (TM = Fe, Co, Ni) GaN monolayers are systematically investigated using density functional theory combined with the nonequilibrium Green’s functions. The TM dopants preserve the semiconducting nature of the GaN monolayer while effectively tuning its bandgap. Notably, the Fe‐doped GaN monolayer exhibits reversible adsorption toward H ₂ S with a reasonable recovery time of 32.7 s at 500 K, indicating its great potential as a reusable H ₂ S sensor, while demonstrating strong chemisorption toward SO ₂ , SOF ₂ , and SO ₂ F ₂ with pronounced bandgap alterations. Electronic transport simulations based on a Fe‐doped GaN field‐effect transistor model further demonstrate superior sensitivity and selectivity toward these gases. In particular, distinct negative differential resistance behaviors and pronounced current responses provide a viable electronic fingerprint for discriminating specific SF ₆ decomposition products. These findings provide valuable theoretical guidelines for designing 2D GaN‐based gas sensors for fault diagnostics in high‐voltage equipment.