Supercritical nitrogen-enhanced interface control for high-frequency T-gate GaN HEMTs fabricated on 8-inch CMOS-compatible wafer

This study demonstrates a large-area, high-performance RF T-gate GaN HEMT fabricated using an 8-inch CMOS back-end-of-line (BEOL)-compatible process. This compatibility enables the efficient integration of GaN-based RF components with CMOS circuits, thereby enhancing overall functionality for next-generation applications in advanced electronics and packaging. To improve the DC and RF performance of the RF device, supercritical fluid nitrogen (SCFN) treatment was applied and optimized at 250 °C for 30 min, effectively reducing trap states on both the AlGaN surface and the AlGaN/GaN interface. Under the optimized condition, the SCFN-treated device exhibited a 21 % increase in maximum drain current (I_DSon,max) by 21 %, a 13 % increase in maximum transconductance (g_m,max), a 59 % reduction in subthreshold swing (SS), and a 40 % reduction in on-resistance (R_on). The device also achieved a notably low drain-induced barrier lowering (DIBL) of 92 mV/V, compared with 175 mV/V for the untreated device. Furthermore, RF performance was substantially improved, with the SCFN-treated device achieving f_T/f_max values of 60/101 GHz—outperforming the 49/72 GHz in untreated devices, at a T-gate length of 0.18 μm. To further clarify these enhancements, a TCAD simulation was conducted to analyze electron trapping in the drift region (gate-drain access region) and its impact on band bending and partial depletion of the two-dimensional electron gas (2DEG). These results provide a comprehensive understanding of the mechanisms driving the observed performance improvement.