Analysis of the electrical properties and current transportation mechanism of a metal oxide semiconductor (MOS) capacitor based on HfGdO gate dielectrics

The microstructure, optical and electrical properties of sputtering-derived HfGdO high-k gate dielectric thin films as a function of the Gd doping content have been systematically investigated. X-ray diffraction (XRD) measurements have indicated that Gd doping can form a new stable cubic phase. The optical band gap of the HfGdO gate dielectrics increases gradually from 5.82 to 6.14 eV as the Gd doping concentration increases. The electrical properties, such as permittivity, oxide trapped charge density, border trap charge density and leakage current density of samples, are determined using a semiconductor device analyzer. The formation mechanism of leakage current is also discussed in detail. In addition, the interfacial properties of HfGdO/Si gate satcks were tested to establish the electrical properties. The excellent optoelectronic properties, such as the optical band gap of 5.95 eV, leakage current density of 8.33 × 10−8 A/cm2 at a bias voltage of 2 V, oxide trapped charge density of −1.06 × 1012 cm−2 and a border trap charge density of zero and optimized interfacial properties were observed in the HfGdO thin films with sputtering power of 30 W, indicating that it may become a potential high-k gate dielectric in future complementary metal oxide semiconductor (CMOS) devices.