Leakage current conduction mechanism of Au-Pt-Ti/ HfO₂-Al₂O₃/n-InAlAs metal-oxide-semiconductor capacitor under reverse-biased condition

Au-Pt-Ti/high-k/n-InAlAs metal-oxide-semiconductor (MOS) capacitors with HfO₂-Al₂O₃ laminated dielectric were fabricated. We found that a Schottky emission leakage mechanism dominates the low bias conditions and Fowler-Nordheim tunneling became the main leakage mechanism at high fields with reverse biased condition. The sample with HfO₂ (4 m)/Al₂O₃ (8 nm) laminated dielectric shows a high barrier height ϕ_B of 1.66 eV at 30 °C which was extracted from the Schottky emission mechanism, and this can be explained by fewer In-O and As-O states on the interface, as detected by the X-ray photoelectron spectroscopy test. These effects result in HfO₂ (4 m)/Al₂O₃ (8 nm)/n-InAlAs MOS-capacitors presenting a low leakage current density of below 1.8 × 10^-7 A/cm² from -3 to 0 V at 30 °C. It is demonstrated that the HfO₂/Al₂O₃ laminated dielectric with a thicker Al₂O₃ film of 8 nm is an optimized design to be the high-k dielectric used in Au-Pt-Ti/HfO₂-Al₂O₃/InAlAs MOS capacitor applications.