Abstract Emerging wide bandgap BAlN alloys have potential for improved III-nitride power devices, including high electron mobility transistors (HEMTs). Yet, few relevant studies have been carried out. In this work, we have investigated the use of the B_0.14Al_0.86N alloy as part or the entirety of the interlayer between the GaN buffer and the AlGaN barrier in the conventional GaN/AlGaN heterostructure. The numerical results show considerable improvement of the two-dimensional electron gas (2DEG) concentration with small 2DEG leakage into the ternary layer by replacing the conventional AlN interlayer by either the B_0.14Al_0.86N interlayer or the B_0.14Al_0.86N/AlN hybrid interlayer. Consequently, the transfer characteristics can be improved. The saturation current can be enhanced as well. For instance, the saturation currents for HEMTs with the 0.5 nm B_0.14Al_0.86N/0.5 nm AlN hybrid interlayer and the 1 nm B_0.14Al_0.86N interlayer are 5.8% and 2.2% higher than that for the AlN interlayer when V_GS−V_th = +3 V.