Low Noise Metamorphic HEMTs with Reflowed Submicron T-Gate

A submicron T-gate fabricated using E- beam lithography and thermally reflow process was developed and was applied to the manufacture of the low noise metamorphic high electron-mobility transistors (MHEMTs). The In0.53Al0.47As/InGaAs MHEMT uses InxAl1-xAs as the buffer layer between GaAs substrate and the InP lattice-matched HEMT structure. The T-gate developed has a gate length of 0.13 µm formed by thermally reflowed technology. The fabricated MHEMT has a saturation drain current of 200 mA/mm and a transconductance of 750 mS/mm at VDS = 1.2V. The noise figure for the 160 µm gate-width device is less than 1 dB and the associated gain is up to 14 dB at 18 GHz. The device demonstrates a cut-off frequency fT of 154 GHz and a maximum frequency fmax of 300 GHz.