Radiation effects of heavy ions in hydrogen-terminated diamond field-effect transistors

Hydrogen-terminated diamond field-effect transistors (H-diamond FETs) are promising for radiation-tolerant electronics, but the response of the Al2O3/H-diamond gate stack to swift heavy ions remains insufficiently understood. Here, H-diamond FETs were irradiated with 1260 MeV Kr+ ions at fluences ranging from 1 × 106 to 1 × 108 ions/cm2 under different gate-bias conditions. DC, gate leakage, C–V, transient, and deep-level transient spectroscopy (DLTS) measurements were performed to evaluate device degradation. As the fluence increased, the threshold-voltage shift (ΔVth) increased from 2.50 ± 0.17 to 11.50 ± 0.51 V, while the relative transconductance reduction increased from 19.51% ± 1.12% to 65.16% ± 0.60%. At 1 × 108 ions/cm2, the subthreshold swing increased from approximately 0.240 to 0.400 ± 0.014 V/dec, and the 90% rise time increased from 0.24 to 0.44 ms. Degradation was more pronounced under positive gate bias during irradiation, suggesting field-assisted charge trapping. The increased gate leakage, C–V distortion, and 3.7-fold enhancement of the DLTS signal are consistent with irradiation-induced trapped charge and electrically active defects in the gate stack. These results identify gate-dielectric charge stability and Al2O3/H-diamond interface quality as key targets for radiation hardening.