Interfacial and electrical characteristics of a HfO₂/n-InAlAs MOS-capacitor with different dielectric thicknesses

A HfO₂/n-InAlAs MOS-capacitor has the advantage of reducing the serious gate leakage current when it is adopted in InAs/AlSb HEMT instead of the conventional Schottky-gate. In this paper, three kinds of HfO₂/n-InAlAs MOS-capacitor samples with different HfO₂ thickness values of 6, 8, and 10 nm are fabricated and used to investigate the interfacial and electrical characteristics. As the thickness is increased, the equivalent dielectric constant ε _ox of HfO₂ layer is enhanced and the InAlAs-HfO₂ interface trap density D_it is reduced, leading to an effective reduction of the leakage current. It is found that the HfO₂ thickness of 10 nm is a suitable value to satisfy the demands of most applications of a HfO₂/n-InAlAs MOS-capacitor, with a sufficiently low leakage current compromised with the threshold voltage.