High linearity AlGaN/GaN HEMT with double- Vth coupling for millimeter-wave applications

We demonstrated an AlGaN/GaN high electron mobility transistor (HEMT) namely double-Vth coupling HEMT (DVC-HEMT) fabricated by connecting different threshold voltage (Vth) values including the slant recess element and planar element in parallel along the gate width with N2O plasma treatment on the gate region. The comparative studies of DVC-HEMT and Fin-like HEMT fabricated on the same wafer show significantly improved linearity of transconductance (G(m)) and radio frequency (RF) output signal characteristics in DVC-HEMT. The fabricated device shows the transconductance plateau larger than 7 V, which yields a flattened f(T)/f(max)-gate bias dependence. At the operating frequency of 30 GHz, the peak power-added efficiency (PAE) of 41% accompanied by the power density (P-out) of 5.3 W/mm. Furthermore, the proposed architecture also features an exceptional linearity performance with 1-dB compression point (P (1 dB)) of 28 dBm, whereas that of the Fin-like HEMT is 25.2 dBm. The device demonstrated in this article has great potential to be a new paradigm for millimeter-wave application where high linearity is essential.