Fabrication of InAlAs/InGaAs high-electron-mobility transistors using ArF-excimer-laser-assisted damage-free highly selective InGaAs/InAlAs etching

Highly selective etching of InGaAs/InAlAs assisted by a 193 nm ArF excimer laser in HBr and F 2 atmosphere is used as a gate-recess technique to fabricate InAlAs/InGaAs high-electron-mobility transistors (HEMTs). The HEMT with an Al/Ti gate shows a gate ideality factor of 1.2 and an effective Schottky barrier height of 0.55 eV. For a 0.7 µ m×18 µ m device, a maximum extrinsic transconductance of 610 mS/mm is obtained. The extrinsic transconductance of the HEMT is stable for more than 6 weeks, whereas degradation of the extrinsic transconductance is observed in a device fabricated by etching using citric acid. Enhancement of InGaAs/InAlAs selectivity is caused by formation of a nonvolatile AlF x thin layer on the InAlAs surface, as shown by the X-ray photoemission spectroscopy (XPS) measurements. The good gate electrical characteristics and long-term transconductance stability are attributed to the Al deficiency of the etched surface after the postetching wash. These results demonstrate that this excimer-laser-assisted selective-etching technique is useful for fabricating damage-free, high-performance InAlAs/InGaAs HEMTs.