A new single event burnout (SEB) hardened AlGaN/GaN structure with a thin barrier interlayer (IL) is presented in this work. The proposed hardened structure is compared with the simulation results of the conventional structure. The comparative analysis demonstrates that the IL lifts the conduction band energy in buffer layer and a new quantum well is formed. The quantum well limits the electrons induced by heavy ion below the second channel into the first channel. Thus, better SEB performance is achieved compared with the conventional structure. Moreover, the breakdown characteristic of the new structure is significantly improved, while the output characteristic is slightly reduced. Under the condition that the two structures are irradiated vertically by heavy ion having the linear energy transfer (LET) value of 0.6 pC/ $\mu \text{m}$ , the SEB threshold voltage of the conventional structure is 280 V, while the hardened structure can achieve 375 V.