Comparison of the Physical and Electrical Properties of HfO₂/Al₂O₃/HfO₂/GeO/Ge and HfO₂/Al₂O₃/GeO/Ge Gate Stacks.

A high-quality HfGeO interfacial layer (IL) was formed in a HfO₂/Al₂O₃/HfO₂/GeO gate stack through thermal annealing. The diffusing of GeO into the HfO₂ layer led to the mixing of the GeO and HfO₂ layers, as identified through energy-dispersive X-ray Spectroscopy (EDX). X-ray photo-electron spectroscopy (XPS) data for HfGeO IL confirmed the formation of Ge-O-Hf bonds owing to the induced shift of the Ge3d spectra to lower binding energies. The electrical and reliability data indicated that the capacitor with HfGeO IL presented not only lower interface states density (Dit, approximately 7 × 10 eVcm) but also less Dit increment (approximately 3 × 10 eVcm) after stressing than did the capacitor without the HfGeO IL. Moreover, the Ge p-metal-oxide-semiconductor field-effect transistor HfGeO IL exhibited a high effective hole mobility (approximately 704 cm2/V s).