Research On The Effect Of Proton Irradiation On AlGaN/GaN Heterostructure

Based on the excellent characteristics of Gallium nitride(Ga N)materials and heterostructures,AlGaN/GaN high electron mobility transistors(HEMT)has the characteristics of large current density,high operating voltage and fast frequency.Therefore,it is widely used in high frequency and high power fields.In particular,the anti-radiation characteristics of Ga N materials are outstanding,so Ga N-based HEMT devices have huge potential and demand in the space field.However,the current research on the irradiation of Ga N-based HEMT devices is still lack of systematicity,which seriously hinders its wide application in the space field.Based on the previous research work,this paper focuses on the comprehensive study of the degradation effects of AlGaN/GaN heterostructures under proton irradiation.Firstly,the effect of proton irradiation on Metal/Al Ga N interface in AlGaN/GaN heterostructure was studied.Proton irradiation experiments with different doses under 3Me V conditions were carried out based on the depletion HEMT devices prepared by ourselves.The characterization of interface defects is completed by frequency-dependent conductance technique based on capacitance test.The experiment found that with increasing radiation dose,the Metal/Al Ga N interface trap energy level becomes shallower,the trap density decreases,and the time constant increases.Especially at the dose of 5×10¹⁴H⁺/cm²,the change of trap density is very obvious,the deepest level is reduced from2.37×10¹⁵cm^-2·e V^-1 to 8.23×10¹⁴cm^-2·e V^-1,which is reduced by 65%;and the shallowest level is decreased from 3.06×10¹⁴cm^-2·e V^-1 to 2.11×10¹³cm^-2·e V^-1,which is reduced by93%.This is obviously different from the changes observed in the AlGaN/GaN heterojunction interface traps in the previous period after irradiation.The changes of the interface morphology before and after proton irradiation were compared by scanning electron microscope(SEM)and transmission electron microscopy(TEM).The results show that there is no obvious change in the Metal/Al Ga N interface morphology before and after irradiation,and there is no obvious migration of elements through energy dispersive X-ray spectroscopy(EDS).In order to verify the above results in depth,the paper compares the reverse gate leakage of the above structure before and after irradiation.It was found that the reverse gate leakage significantly decreased after irradiation,which was consistent with the observed decrease in trap density.Further experiments were conducted to apply positive gate stress on the basis of irradiation.The results show that the irradiation treatment device has a lower trap density and a shallower energy level than the Fresh device on Metal/Al Ga N interface after electrical stress.Moreover,the positive gate stress can reduce the interface energy level distribution range,and proton irradiation can enhance this effect.Proton irradiation of enhanced HEMT and MIS-HEMT devices is further studied.After the irradiation of the enhanced HEMT device,the change rules of Metal/Al Ga N and AlGaN/GaN interface traps are similar of the depletion device.However,compared with the Coulomb effect,the effect of increased carrier concentration at the channel dominates,resulting in negative drift of C-V characteristics after irradiation.Further extraction of the square resistance calculations revealed that the mobility decreased after irradiation.The two interface traps of the MIS-HEMT device show different rules of the depletion device after irradiation.And the trap density of the AlGaN/GaN interface is lower than that of conventional devices after irradiation.It shows that the passivation treatment has a certain blocking effect on the protons,which is a good method for device strengthening.Finally,the typical degradation phenomenon of three-terminal device after proton irradiation is analyzed.And the impact of irradiation is clearly defined from the perspective of series resistance,ohmic contact resistance,and leakage current.Further,the effect of changes in transverse size of the device on the radiation effect was studied by using different devices of gate-source and gate-drain spacing.Moreover,the effect of irradiation on the vacancy density in devices with different longitudinal size of Al Ga N barrier layer was simulated by SRIM software.The variation of vacancy density of each element with depth was also observed.In addition,by comparing the passivation treatment of devices with 4 different materials through simulation,we found that Al N has a relatively better anti-irradiation effect,and the effect of different passivation layer thickness on the anti-irradiation characteristics of devices was explored.