Electrical Properties of HfTiON Gate-Dielectric GaAs Metal-Oxide-Semiconductor Capacitor With AlON as Interlayer

High- k HfTiON gate-dielectric GaAs MOS capacitors with and without AlON as interfacial passivation layer (IPL) are fabricated and their interfacial and electrical properties are compared. It is found that low interface-state density ( 1.5×10¹² cm^-2eV^-1 at midgap), small gate leakage current ( 1.3×10^-4 A/cm² at Vg=Vfb+1 V), small capacitance equivalent thickness (1.72 nm), large equivalent dielectric constant (25.6), and high device reliability can be achieved for the Al/HfTiON/AlON/GaAs MOS device. All of these should be due to the fact that the AlON IPL on sulfur-passivated GaAs can effectively reduce the density of defective states and unpin the Femi level at the AlON/GaAs interface, thus greatly improving the interfacial and electrical properties of the device.