A Graded-Gate Structure of AlN/GaN HEMT for High-Linearity Applications

In this article, a high-linearity AlN/GaN high-electron-mobility transistor with graded-gate length along the gate width direction was demonstrated. The device is used in high-linearity applications by employing a structure with a graded-gate length along the gate width direction. The graded-gate structure is achieved by using the method of over-development technology. As results show, by changing the appropriate process conditions such as development time, the fabricated graded-gate length structure has a significant impact in optimizing the transconductance profile, thereby improving the linearity of GaN HEMTs. The device exhibits an Id,maxof 1735 mA/mm, a gm,maxof 273 mS/mm with a gate voltage swing of the transconductance plateau up to 5.5 V and a difference in peak extrinsic transconductance of 1.85 mS/mm. In addition, the device has a radio frequency (RF) performance of fT/fmax=89/150 GHz for an equivalent gate length of 100 nm. The devices fabricated in this article have great potential for improving the linearity of mmWave RF devices, which has significance for future 5G wireless communications.