Study on the physical and leakage current characteristics of an optimized high-k/InAlAs MOS capacitor with a HfO2-Al2O3 laminated dielectric

Abstract

High-k/n-InAlAs MOS capacitors are popular for the isolated gate of InAs/AlSb and InAlAs/InGaAs high-electron mobility transistors. In this study, a new kind of high-k/n-InAlAs MOS-capacitor with a HfO2-Al2O3 laminated dielectric was successfully fabricated using an optimized process. Compared with the traditional HfO2/n-InAlAs MOS capacitor, the new device has a larger equivalent oxide thickness. Two devices, with a HfO2 (8 nm)-Al2O3 (4 nm) laminated dielectric and a HfO2 (4 nm)-Al2O3 (8 nm) laminated dielectric, respectively, were studied in comparison to analyze the effect of the thickness ratios of HfO2 and Al2O3 on the performance of the devices. It was found that the device with a HfO2 (4 nm)-Al2O3 (8 nm) laminated dielectric showed a lower effective density of oxide charges, and an evidently higher conduction band offset, making its leakage current achieve a significantly low value below 10-7 A/cm2 under a bias voltage from -3 to 2 V. It was demonstrated that the HfO2-Al2O3 laminated dielectric with a HfO2 thickness of 4 nm and an Al2O3 thickness of 8 nm improves the performance of the high-k dielectric on InAlAs, which is advantageous for further applications.