InP MOS capacitor and E-mode n-channel FET with ALD Al2O3-based high-k dielectric

The electrical characteristics of atomic-layer-deposited Al2O3/TiO2/Al2O3 on (NH4)(2)S-treated InP MOS capacitor and related MOSFET were studied. The electrical characteristics were improved from the reduction of native oxides and sulfur passivation on InP by (NH4)(2)S treatment. The high bandgap Al2O3 on TiO2 can reduce the thermionic emission, and the Al2O3 under TiO2 improves the interface-state density by self-cleaning. The high dielectric constant TiO2 is used to lower the equivalent oxide thickness. The leakage currents can reach 2.3 9 10(-8) and 2.2 x 10(-7) A/cm(2) at +/- 2 MV/cm, respectively. The lowest interface-state density is 4.6 x 10(11) cm(-2) eV(-1) with a low-frequency dispersion of 15 %. The fabricated enhancement-mode n-channel sulfur-treated InP MOSFET exhibits good electrical characteristics with a maximum transconductance of 146 mS/mm and effective mobility of 1760 cm(2)/V s. The subthreshold swing and threshold voltage are 117 mV/decade and 0.44 V, respectively.