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采用二次外延重掺杂n~+GaN实现非合金欧姆接触,并通过优化干法刻蚀和金属有机化学气相沉积(MOCVD)外延工艺,有效降低了欧姆接触电阻。将非合金欧姆接触工艺应用于InAlN/GaN异质结场效应晶体管(HFET)器件制备,器件的有效源漏间距缩小至600 nm。同时,结合40 nm T型栅工艺,制备了高电流截止频率(f_T)和最大振荡频率(f_(max))的InAlN/GaN HFET器件。结果显示减小欧姆接触电阻和栅长后,器件的电学特性,尤其是射频特性得到大幅提升。栅偏压为0 V时,器件最大漏源饱和电流密度达到1.88 A/mm;直流峰值跨导达到681 m S/mm。根据射频小信号测试结果外推得到器件的f_T和f_(max)同为217 GHz。
The non-alloy ohmic contact is realized by the second epitaxy heavily doped n ~ + GaN, and the ohmic contact resistance is effectively reduced by optimizing the dry etching and the metal organic chemical vapor deposition (MOCVD) epitaxy process. The non-alloy ohmic contact process is applied to the fabrication of InAlN / GaN heterojunction field effect transistor (HFET) devices, and the effective source-drain spacing of the device is reduced to 600 nm. At the same time, InAlN / GaN HFET devices with high current cutoff frequency (f_T) and maximum oscillation frequency (f_ (max)) were fabricated with a 40 nm T-gate process. The results show that the reduction of ohmic contact resistance and gate length, the device’s electrical properties, especially the radio frequency characteristics have been greatly improved. When the gate bias voltage is 0 V, the maximum drain current density of the device reaches 1.88 A / mm and the peak value of the dc peak reaches 681 m S / mm. The f_T and f_ (max) obtained by extrapolation of RF small signal test result are 217 GHz.