In-Situ Surface Passivation and Metal-Gate/High-κDielectric Stack Formation for N-channel Gallium Arsenide Metal-Oxide-Semiconductor Field-Effect Transistors

We demonstrate an in-situ surface passivation technique for the formation of high-permittivity gate dielectric on GaAs using a multiple chamber metal-organic chemical vapor deposition (MOCVD) system. In-situ vacuum annealing and SiH₄ treatment were performed prior to high-κ dielectric deposition. This novel passivation scheme effectively suppresses the formation of Ga or As oxide during the high-κ dielectric deposition process. Self-aligned GaAs MOSFETs were fabricated, showing excellent device characteristics with a peak electron mobility of 1244.4 cm²/Vs. The effect of post deposition anneal (PDA) temperature and forming gas anneal (FGA) conditions on the GaAs MOS capacitors was also investigated. Using HfAlO as gate dielectric, the in-situ surface passivated GaAs MOS capacitors demonstrate low frequency dispersion, small hysteresis and low midgap interface state density (D_it) of 2.4 × 10¹¹ to 7.5 × 10¹¹ cm^-2.eV^-1, determined by high frequency conductance method.