电流增益截止频率为236GHz的InAIN/GaN高频HEMT

研制了高电流增益截止频率(fT)的InAlN/GaN高电子迁移率晶体管(HEMT).采用金属有机化学气相沉积(MOCVD)再生长n+GaN非合金欧姆接触工艺将器件源漏间距缩小至600 nm,降低了源、漏寄生电阻,有利于改善器件的寄生效应;使用低压化学气相沉积(LPCVD)生长SiN作为栅下介质,降低了InAlN/GaN HEMT栅漏电;利用电子束光刻实现了栅长为50 nm的T型栅.此外,还讨论了寄生效应对器件fT的影响.测试结果表明,器件的栅漏电为3.8 μA/mm,饱和电流密度为2.5 A/mm,fT达到236 GHz.延时分析表明,器件的寄生延时为0.13 ps,在总延时中所占的比例为19％,优于合金欧姆接触工艺的结果.

High-Frequency InAlN/GaN HEMT with the Current Gain Cutoff Frequency of 236 GHz

InAlN/GaN high electron mobility transistors (HEMTs) with high current gain cutoff frequency (fT) were fabricated.To reduce the drain and source parasitic resistances and depress the parasitic effects of the device,the source-to-drain distance was scaled to 600 nm using the non-alloyed n+ GaN ohmic contacts technology regrown by the metal organic chemical vapor deposition (MOCVD).To reduce the gate leakage current of the InAlN/GaN HEMT,SiN was used as the gate-dielectric layer deposited by the low pressure chemical vapor deposition (LPCVD).Electron beam lithography was employed to define a T-shaped gate with a gate length of 50 nm.In addition,the influence of parasitic effects on fT for the HEMT was discussed.The test results show that the fabricated device achieves a gate leakage current of 3.8 μA/mm,a saturated current density of 2.5 A/mm and afT of 236 GHz.The delay analysis shows that the parasitic delay time of the device is 0.13 ps,which is 19％ of the total delay time,and better than that in the device with the alloyed ohmic contact technology.