AlGaN/GaN HEMT凹栅槽结构器件的频率特性

Frequency Characteristics of AlGaN/GaN HEMT Devices with Recessed Gate Structure

采用一系列不同栅长和结构的T型栅器件来研究凹栅槽结构抑制短沟道效应和提高频率特性的作用。随着栅长不断缩短,短沟道效应逐渐明显,栅长从300 nm缩短至100 nm时,亚阈值摆幅逐渐增大,栅对沟道载流子的控制变弱,且器件出现软夹断现象。凹栅槽结构可以降低器件的亚阈值摆幅,提高开关比,栅长100 nm常规结构器件的亚阈值摆幅为140 mV/dec,开关比为106,而凹栅槽结构器件的亚阈值摆幅下降为95 mV/dec,开关比增大为107,凹栅槽结构明显抑制了短沟道效应。在漏源电压为20 V时,100 nm栅长的凹栅槽结构器件的截止频率和最高振荡频率达到了65.9和191 GHz,同常规结构相比,分别提高了5.78%和4.49%。由于凹栅槽结构缩短了栅金属到二维电子气（2DEG）沟道的间距,增大了纵横比,所以能够改善器件的频率特性。

A series of T-shaped gate devices with different gate lengths and structures were fabricated to investigate the effects of recessed gate structure on reducing the short channel effects and improving the frequency characteristics of the devices. As the gate length shortens,the short channel effects become more and more obvious. When the gate length is shortened from 300 nm to 100 nm,the subthreshold swing gradually increases,and the control of gate on the channel charge becomes weaker with soft pinchoff. Recessed gate structure could reduce the subthreshold swing and improve the switching ratio. The subthreshold swing and switch ratio of conventional structure devices with 100 nm gate length is 140 mV/dec and 106,respectively,while the corresponding parameters of the recessed gate structure device are improved to 95 mV/dec and 107,respectively. At the drain-source voltage of 20 V,compared with the conventional structure,the cut-off frequency and maximum oscillation frequency of 100 nm gate length recessed gate devices reach 65. 9 and 191 GHz（ increasing by 5. 78% and 4. 49% when compared to the regular structure）,respectively. The improved frequency performance of the recessed gate structure isbenefited from the reduced space between the gate metal and two-dimensional electron gas（ 2DEG） channel as well as the increased aspect ratio.