AlN/GaN HEMT毫米波器件结构仿真研究

为实现更高工作频率的氮化镓（gallium nitride,GaN）基高电子迁移率晶体管（high electron mobility transistor,HEMT）器件，采用薄势垒外延结构、缩小栅长对提升器件的截止频率十分重要。通过对不同氮化铝（aluminium nitride,AIN）势垒层厚度以及不同尺寸栅长的AlN/GaN HEMT进行仿真分析，系统研究不同结构对器件短沟道效应、直流及频率等特性的影响。首先固定栅长为100nm，研究了跨导与截止频率随AlN势垒层厚度的变化情况。跨导随势垒层厚度的增加先增大后减小。当势垒层厚度为4nm时，跨导达到最大值(592mS/mm)，截止频率也达到最大值。为尽可能提升器件的截止频率，同时避免器件出现短沟道效应，固定AlN势垒层厚度为4nm，研究器件截止频率与短沟道效应随器件栅长的变化情况。仿真表明器件截止频率随栅长的减小而增大，50nm栅长的器件截止频率最高，但栅长为50nm时器件短沟道效应严重，此时器件纵横比(Lg/Tbar)为12.5。因此需要提升器件的纵横比，当器件栅长达到100nm时(Lg/Tbar=25)，器件短沟道效应得到抑制，且具有较高的截止频率。仿真结果表明，AlN HEMT具有较高的截止频率，同时应采用较大的纵横比设计(纵横比为25左右)以抑制短沟道效应，为后续高频AlN/GaN HEMTs器件的制备提供了理论依据。

Simulation study of AlN/GaN HEMT millimeter wave device structure

In order to realize GaN-based HEMT devices with higher operating frequency, it is very important to use thin barrier epitaxial structure and reduce gate length to improve the cut-off frequency of the device. AlN/GaN HEMTs with different AlN barrier thicknesses and gate lengths are simulated and analyzed to systematically study the effects of different structures on the short-channel effect, DC and frequency characteristics of the device. Firstly, the gate length was fixed to 100nm, and the variation of the transconductance and cutoff frequencies with the thickness of the AlN barrier layer was studied. The transconductance increases first and then decreases with the increase of barrier thickness. When the barrier layer thickness is 4nm, the transconductance reaches its maximum value (592mS/mm), and the cutoff frequency also reaches its maximum value. In order to increase the cutoff frequency of the device as much as possible and avoid short channel effect of the device, the thickness of the AlN barrier layer is fixed at 4nm. The changes of the cutoff frequency and short channel effect with the gate length of the device are studied. The simulation results show that the cutoff frequency of the device increases with the decrease of the gate length. The cutoff frequency of the device with the gate length of 50nm is the highest, but the device has a serious short channel effect when the gate length is 50nm, and the aspect ratio (Lg/Tbar) of the device is 12.5. Therefore, it is necessary to improve the aspect ratio of the device. When the gate length of the device reaches 100nm (Lg/Tbar=25), the short-channel effect of the device is suppressed and the device has a high cut-off frequency. The simulation results show that AlN HEMT have high cutoff frequency and should be designed with a large aspect ratio (about 25) to suppress the short channel effect, which provides a theoretical basis for the subsequent preparation of high-frequency AlN/GaN HEMTs.