Pseudomorphic AlGaAs/InGaAs/GaAs High Electron Mobility Transistors with Super Low Noise Performances of 0.41 dB at 18 GHz

Fully passivated low noise AlGaAs/InGaAs/GaAs pseudomorphic (PM) HEMT with wide head T‐shaped gates were fabricated by dose split electron beam lithography (DSL). The dimensions of gate head and footprint were optimized by controlling the splitted pattern size, dose, and spaces of each pattern. We obtained stable T‐shaped gate of 0.15 μm gate length with 1.35 μm‐wide head. The maximum extrinsic transconductance was 560 mS/mm. The minimum noise figure measured at 18 GHz at Vds = 2 V and Ids = 17 mA was 0.41 dB with associated gain of 8.19 dB. At 12 GHz, the minimum noise figure and an associated gain were 0.26 and 10.25 dB, respectively. These noise figures are the lowest values ever reported for GaAs‐based HEMTs. These results are attributed to the extremely low gate resistance of wide head T‐shaped gate having a ratio of the head to footprint dimensions larger than 9.