Atomic-layer-deposited Al₂O₃ and HfO₂ on InAlAs: A comparative study of interfacial and electrical characteristics

Al₂O₃ and HfO₂ thin films are separately deposited on n-type InAlAs epitaxial layers by using atomic layer deposition (ALD). The interfacial properties are revealed by angle-resolved x-ray photoelectron spectroscopy (AR-XPS). It is demonstrated that the Al₂O₃ layer can reduce interfacial oxidation and trap charge formation. The gate leakage current densities are 1.37×10^-6 A/cm² and 3.22×10^-6A/cm² at +1 V for the Al₂O₃/InAlAs and HfO₂/InAlAs MOS capacitors respectively. Compared with the HfO₂/InAlAs metal-oxide-semiconductor (MOS) capacitor, the Al₂O₃/InAlAs MOS capacitor exhibits good electrical properties in reducing gate leakage current, narrowing down the hysteresis loop, shrinking stretch-out of the C-V characteristics, and significantly reducing the oxide trapped charge (Q_ot) value and the interface state density (D_it).