The ultra-wide bandgap semiconductor β-Ga₂O₃ is a promising material for next-generation optoelectronic systems and hybrid nanodevices. However, high interface state densities and anomalous trap-assisted leakage severely restrict its performance and signal transduction capabilities. To resolve these fundamental limitations, we investigated a two-dimensional h-BN interlayer to construct a high-quality heterogeneous metal/h-BN/β-Ga₂O₃ structure using experimentally calibrated Sentaurus TCAD simulations. Energy-band analysis and validated I–V simulations reveal that the low-dimensional h-BN interlayer reconstructs the interfacial barrier, suppresses interface-assisted recombination, and shifts the dominant carrier transport from thermionic emission to Fowler–Nordheim tunneling. These effects markedly reduce the interface-state density and effectively suppress the Shockley–Read–Hall recombination current, mechanisms that are critical for minimizing dark current and improving device sensitivity. After systematically examining the effects of key parameters on the electrical characteristics of this hybrid architecture, we quantify the tradeoff between threshold voltage and on-resistance using a comprehensive figure of merit. Specifically, our results indicate that maximum device efficiency is achieved only when an optimal h-BN thickness of 3.56–5.88 nm (10–17 atomic layers) is strategically integrated with the appropriate metal work function and semiconductor doping. Overall, this work suggests the potential advantage of 2D h-BN in mitigating the interfacial bottleneck of traditional β-Ga₂O₃ platforms, providing quantitative design guidelines and theoretical support for the heterogeneous integration of next-generation optoelectronic devices.