Electrical characteristics of GaAs MOS capacitor and field effect transistor with atomic layer-deposited TiO2/Al2O3 dielectrics

The (NH4)2S treatment can reduce native oxides and passivate GaAs. Atomic layer-deposited Al2O3 can further remove the residue native oxides by self-cleaning. Stacked with high dielectric constant TiO2 prepared by atomic layer deposition on Al2O3/(NH4)2S-treated GaAs MOS capacitor, the leakage current densities can reach 4.5 × 10−8 and 3.4 × 10−6 A/cm2 at ±2 MV/cm. The net effective dielectric constant of the entire stack is 18 and the interface state density is about 4.2 × 1011/cm2/eV. The fabricated enhancement-mode n-channel GaAs MOSFET exhibited good electrical characteristics with a maximum gm of 122 mS/mm and electron mobility of 226 cm2/V s.