Investigation of multi-fingers drain field plate in dual-threshold coupling AlGaN/GaN high electron mobility transistors for optimizing linearity at high electrical fields in the Ka band

GaN high electron mobility transistors were fabricated and investigated in detail to improve their linearity at high operating voltage. The scheme of dual-threshold (DT) coupling was adopted to mitigate the transconductance (G (m)) nonlinearity and a multi-fingers drain field plate (MF-DFP) was employed to alleviate the high electric field. The proposed GaN HEMT, integrating the DT technique (DT HEMT) and MF-DFP structure (DT HEMT W/ MF-DFP), yielded a G (m) plateau of & SIM;5.5 V and a & SIM;8 dB improvement in the calculated output third-order intercept point(OIP3) than that of DT HEMT. The load-pull measurements at 30 GHz delivered a peak power-added efficiency (PAE) of 52.5 % at V (ds) = 10 V, and saturation output power density (P (out)) of 5.5 W mm(-1) at V (ds) = 20 V. In comparison with the DT HEMT, the DT HEMT W/ MF-DFP obtained a flatter gain profile, with & SIM;1.5 dB improvement in gain compression at V (ds) = 20 V.