Improved Linearity Performance at High Operation Voltage on Dual-threshold Coupling AlGaN/GaN HEMTs by Modulating the Duty Ratio

In this work, high linearity AlGaN/GaN HEMTs accomplished by implementing the dual-threshold coupling technique (DT HEMTs) have been studied. It was found that the transconductance (G(m)) profile for DT HEMTs at high operation voltage was sever compressed induced by the high electric field (E-field), and the phenomenon could be optimized by modulating the alpha, which was defined as the duty ratio of planar- and recess-elements in a period width. Consequently, the fabricated composite device with alpha = 0.7 yielded the gate voltage swing (GVS-G(m)) of 4.5 V at V-ds = 6 V, while GVS-G(m) of 3.97 V at V-ds = 25 V was obtained by DT HEMTs whose alpha is 0.5. Meanwhile, For the DT HEMTs with alpha = 0.5, the predicted output third-order intercept (OIP3) of 39 dBm among a wide gate voltage range at V-ds = 25 V was achieved, and the large signal performance at 8 GHz delivered P-out of 4.7 W/mm with 1.9 dB improvement in gain compression (G(com)), and 2 dB enhancement in 1-dB compression point (P1-dB), respectively, at V-ds = 25V. The suppressed G(com) and enhanced P1-dB indicates that the DT HEMTs with alpha = 0.5 is capable for linearity requirements at high operation voltage.