AlGaN/GaN高电子迁移率晶体管器件电离辐照损伤机理及偏置相关性研究

本文利用 60Co γ射线,针对 AlGaN/GaN高电子迁移率晶体管(high-electron mobility transistors,HEMT)器件,开展了在不同偏置下器件电离辐照总剂量效应实验研究.采用1/f噪声结合直流电学特性参数对实验结果进行测量分析,分析结果表明,受到辐照诱生氧化物缺陷电荷与界面态的影响,当辐照总剂量达到1 Mrad(Si)时,零偏条件下AlGaN/GaN HEMT器件的电学参数退化得最大,其中,饱和漏电流减小36.28%,最高跨导降低52.94%;基于McWhorter模型提取了AlGaN/GaN HEMT器件辐照前后的缺陷密度,零偏条件下辐照前后缺陷密度变化最大,分别为4.080 × 1017和6.621 × 1017 cm–3·eV–1.其损伤机理是在氧化物层内诱生缺陷电荷和界面态,使AlGaN/GaN HEMT器件的平带电压噪声功率谱密度增加.

Ionizing radiation damage mechanism and biases correlation of AlGaN/GaN high electron mobility transistor devices

In this paper,the total dose effect on AlGaN/GaN high-electron-mobility transistor(HEMT)devices after60Coγ-ray irradiation with a total dose of 1 Mrad(Si)was investigated at different biases(FGS=-3 V,FDS=0.5 V;VGS=-1.9 V,VDS=0.5 V;VGS=0 V,VDS=0 V).The experimental results were analyzed using 1/f low-frequency noise and direct current electrical characteristics.The electrical parameters degraded mostly under zero bias condition because of the radiation-induced defect charge of the oxide layer and the interface state.Wherein,the saturation drain current was reduced by 36.28%,and the maximum transconductance was reduced by 52.94%.The reason was that the oxide dielectric layer of AlGaN/GaN HEMT devices generated electron-hole pairs underγ-ray irradiation,and most of the electrons were quickly swept out of the oxide region corresponding to the gate-source and gate-drain spacer regions,and most of the holes remained in the oxide.Under the action of the built-in electric field,holes slowly moved towards the interface between the oxide and AlGaN,which depleted the two-dimensional electron gas of the channel.According to the McWhorter model,the low-frequency noise in the AlGaN/GaN HEMT devices results from random fluctuations of carriers,which are caused by the capture and release processes of carriers by traps and defect states in the barrier layer.The extracted defect densities in AlGaN/GaN HEMT devices increased from 4.080×1017 cm-3·eV-1 to 6.621×1017cm-3·eV-1 under the condition of zero bias,and the result was in good agreement with test results of the direct currentelectrical characteristics.The damage mechanism was the radiation-induced defect charge in the oxide layer and the interface state,which increased the flat-band voltage noise power spectral density of the AlGaN/GaN HEMT devices.According to the charge tunneling mechanism,the spatial distribution of defect in the barrier layer was extracted,and the result also proved that the densities of radiation-induced defect charges under zero bias were more than the other biases.The experimental results showed that zero bias was the worst bias for AlGaN/GaN HEMT devices irradiation.