A Novel Concept of using Double Threshold Voltage Coupling to Improve the linearity of AlGaN/GaN HEMTs for millimeter-wave applications

In this letter, we demonstrate an AlGaN/GaN HEMT fabricated by synthesizing recess and planar devices along the gate width and incorporating N2O plasma treatment to form an oxide layer at the gate electrode of the proposed HEMT. The transconductance curve of the fabricated device has a plateau region larger than 7 V, with a flattened response curve of fT/fmaxwith respect to the gate bias voltage. At the operating frequency of 30 GHz, the maximum power-added efficiency (PAE) is 41%, the value of the power density ($\mathrm{P}_{\mathrm{o}\mathrm{u}\mathrm{t}}$ is 5.3 W/mm, and the associated 1dB compression point $(\mathrm{p}_{\mathrm{l}\mathrm{d}\mathrm{B}^{)}}$ is 28 dBm. The device presented in this article has excellent potential for millimeter-wave applications where high linearity is essential.