Improved Interfacial and Electrical Properties of GaAs MOS Capacitor With LaON/TiON Multilayer Composite Gate Dielectric and LaON as Interfacial Passivation Layer

GaAs metal-oxide-semiconductor capacitors are fabricated by alternately depositing La oxynitride (LaON)/TiON or TiON/LaON or first depositing a LaON interlayer and then alternately depositing LaON/TiON, and their interfacial and electrical properties are investigated and compared. Experimental results show that the sample with LaON interlayer exhibits better interface quality and electrical performance than the other two samples: lower interface-state density (1.05×10
¹²
cm
^-2
eV
^-1
), smaller gate leakage current (2.33 × 10
^-5
A/cm
²
at Vfb + 1 V), larger equivalent dielectric constant (25.3), and better high-field reliability. The involved mechanism lies in the fact that the LaON interlayer on the GaAs surface can effectively reduce the defective states at/near the interface by blocking the Ti/O in-diffusion and As/Ga out-diffusion, thus improving the interfacial and electrical properties of the device.