Fabrication of 150-nm T-Gate Metamorphic AlInAs/GaInAs HEMTs on GaAs Substrates by MOCVD

Metamorphic AlInAs/GaInAs high-electron-mobility transistors (HEMTs) of 150-nm gate length with very good device performance have been grown by metal-organic chemical vapor deposition, with the introduction of an effective multistage buffering scheme. By using a combined optical and e-beam photolithography technology, submicrometer mHEMT devices have been achieved. The devices exhibit good dc and RF performance. The maximum transconductance was 1074 mS/mm. The nonalloyed ohmic contact resistance Rc was as low as 0.02 Ω·mm. The unity current gain cutoff frequency (fT) and the maximum oscillation frequency (f_max) were 279 and 231 GHz, respectively. This device has the highest fT yet reported for 150-nm gate-length HEMTs. Also, an input capacitance to gate-drain feedback capacitance ratio C_gs/C_gd of 3.2 is obtained in the device.