Suppression of GeO _x interfacial layer and enhancement of the electrical performance of the high- K gate stack by the atomic-layer-deposited AlN buffer layer on Ge metal-oxide-semiconductor devices

For high-performance nanoscale Ge-based transistors, one important point of focus is interfacial germanium oxide (GeO _x ), which is thermodynamically unstable and easily desorbed. In this study, an atomic-layer-deposited AlN buffer layer was introduced between the crystalline ZrO₂ high-K gate dielectrics and epitaxial Ge, in order to reduce the formation of interfacial GeO _x . The results of X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy demonstrate that the AlN buffer layer suppressed the formation of interfacial GeO _x . Hence, significant enhancement of the electrical characteristics of Ge metal-oxide-semiconductor (MOS) capacitors was achieved with a two-orders-of-magnitude reduction in the gate leakage current, a 34% enhancement of the MOS capacitance, and a lower interfacial state density. The results indicate that the AlN buffer layer is effective in providing a high-quality interface to improve the electrical performance of advanced Ge MOS devices.