Annealing temperature dependence of interface characteristic and energy-band alignment in ultra-thin HfLaO/Si and HfLaO/SiGe interfaces

The interface characteristic and energy band alignment of HfLaO/Si and HfLaO/Si0.75Ge0.25 interface with and without annealing are studied by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The results show that the thickness of the interfacial layer (IL) for HfLaO grown on SiGe substrate is thinner than that on Si substrate after RTA at 950 °C, which is due to the formation of Ge-rich layer (GRL). The valence band offsets (VBOs) ΔEv of as-grown HfLaO/Si and HfLaO/Si after annealing at 550 and 950 °C are determined to be 2.73 ± 0.01, 3.06 ± 0.01, and 3.17 ± 0.01 eV, respectively. While, the VBOs of as-grown HfLaO/SiGe and HfLaO/SiGe after annealing at 550 and 950 °C are found to be 3.06 ± 0.02, 3.23 ± 0.02, and 3.34 ± 0.02 eV, respectively. The monotonous increase of VBO with the rise of annealing temperature is due to an enhanced electrostatic dipole field between the oxide and the substrate for annealed sample. The VBO of the HfLaO/SiGe is higher than that of the HfLaO/Si system, which would make HfLaO/SiGe suitable for the fabrication of the p-channel MOSFETs.