Bilayer metal oxide gate insulators for scaled Ge-channel metal-oxide-semiconductor devices

We investigate the electrical properties of germanium-channel metal-oxide-semiconductor capacitors with an amorphous atomic-layer-deposited (ALD)-Al(2)O(3) interlayer (IL) and higher-k ALD-TiO(2) gate dielectric. An ALD-Al(2)O(3) IL of similar to 1 nm thickness reduces the gate leakage current density at the otherwise low band-offset TiO(2)/Ge interface by six orders of magnitude at flatband. Devices with the thinnest Al(2)O(3) IL exhibited a low capacitance equivalent thickness of 1.2 nm. The hysteresis of the capacitance-voltage curves was < 10 mV for TiO(2)/Al(2)O(3)/Ge capacitors with different Al(2)O(3) thicknesses. We obtained a relatively low minimum density of interface states, D(it) similar to 3x10(11) cm(-2) eV(-1), suggesting the potential of Al(2)O(3) ILs for higher-k/Ge interface passivation.