Improved electrical properties of GaAs MOS capacitor by using HfLaON passivation layer

GaAs MOS capacitor with HfLaON as passivation layer and HfTiON as gate dielectric is fabricated and compared with its counterparts with LaON as passivation layer and no passivation layer. Results show that the sample exhibits better electrical properties: smaller hysteresis, higher k value (23.87), lower interface state density (9×10
^-5
cm
^-2
eV
^-1
), lower leakage current (4.37×10
^-5
A/cm
²
at Vfb+1V), smaller frequency dispersion and better high-field reliability. These should be ascribed to the capability of the passivation layer in suppressing the out-diffusion of Ga/As to the dielectric and in-diffusion of Hf/Ti/O to the substrate, thus reducing defective states to unpin the Fermi level at the dielectric/GaAs interface. Better passivation effect of HfLaON than LaON should be due to the reduced hygroscopicity of LaON by Hf incorporation.