Study on displacement damage effect of highly charged ions in carbon nanotube field-effect transistor

Based on carbon nanotube (CNT) field-effect transistors (FETs), integrated circuits in next generation have broad application prospects in space exploration. However, the displacement damage (DD) effect is considered as an important factor which limits the performance of CNTFETs. In this study, the local bottom-gate CNTFETs with different channel sizes have been irradiated by highly charged ions (HCI)-132Xe20+ with of energy 5 MeV, the fluences ranged from 1 × 1011 ions/cm2 to 2 × 1015 ions/cm2. At low fluences (1 × 1011, 1 × 1012 and 1 × 1013 ions/cm2), the on/off ratio and transconductance of CNTFETs decreased, and the threshold voltage shift negatively. The reason was HCI introduced defects in the gate dielectric and CNT layer, resulting in reducing carrier mobility, thereby decreasing the on/off ratio and transconductance of CNTFETs. In addition, the interface states and bulk traps in the gate dielectric layer would capture ionized holes to form charge state defects, causing the threshold voltage to shift negatively, and the degree of drift was related to the channel size L/W. At high fluences (1 × 1014, 1 × 1015 and 2 × 1015 ions/cm2), the source and drain of CNTFETs were turned on, the device failed, and the gate leakage current increased. As the irradiation fluence increased, the D-band appeared in the Raman spectrum of SWCNT, the intensity ratio of the D-band and the G+-band increased, and the linear shape of the G--band changed. The irradiation fluence exceeded 1 × 1013 ions/cm2, the Raman peaks overlapped, and the SWCNT became amorphous. AFM images showed that when the irradiation fluence was 1 × 1013 ions/cm2, the SWCNT was complete. When the fluence was increased to 1 × 1015 ions/cm2, the SWCNT was broken. The study showed that the DD tolerance of CNTFETs could reach 1 × 1013 ions/cm2, which proved the excellent radiation resistance of CNTFETs and provided a reference for the radiation resistance of CNT-based microelectronic devices.