AHfO2/n–In Al As MOS-capacitor has the advantage of reducing the serious gate leakage current when it is adopted in In As/Al Sb HEMT instead of the conventional Schottky-gate. In this paper, three kinds of Hf O2/n–In Al As MOS-capacitor samples with different Hf O2 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 Hf O2 layer is enhanced and the In AlAs-HfO2 interface trap density Ditis reduced, leading to an effective reduction of the leakage current. It is found that the Hf O2 thickness of 10 nm is a suitable value to satisfy the demands of most applications of a HfO2/n–In Al As MOS-capacitor, with a sufficiently low leakage current compromised with the threshold voltage.
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