Low-density drain high-electron mobility transistors(LDD-HEMTs) with different F plasma treatment were investigated by simulations and experiments.The LDD region was performed by introducing negatively charged fluorine ions,which modified the surface field distribution on the drain side of the HEMT,and the enhancement of breakdown voltage were achieved.With the increased fluorine plasma treatment power and LDD region length,the breakdown voltage can be maximumly improved by 70%,and no severe reductions on output current and transconductance were observed.To confirm the temperature stability of the devices,annealing experiments were carried out at 400 ℃ for 2 min in ambient N_2.Moreover,the gate leakage current and breakdown voltage before and after annealing were compared and analyzed,respectively. Low-density drain high-electron mobility transistors (LDD-HEMTs) with different F plasma treatment were investigated by simulations and experiments. The LDD region was conducted by introducing negatively charged fluorine ions, which modified the surface field distribution on the drain side of the HEMT, and the enhancement of breakdown voltage were achieved. Since the increased fluorine plasma treatment power and LDD region length, the breakdown voltage can be mostly improved by 70%, and no severe reductions on output current and transconductance were observed. To confirm the temperature stability of the devices, annealing experiments were carried out at 400 ° C for 2 min in ambient N_2.Moreover, the gate leakage current and breakdown voltage before and after annealing were compared and analyzed, respectively.