Germanium metal-insulator-semiconductor capacitors with rare earth La2O3 gate dielectric

In this work, we investigate La"2O"3 as a gate dielectric candidate for Ge devices, using metal-insulator-semiconductor (MIS) structures. When the deposition temperature increases, the electrical characteristics improve with regard to dispersion in accumulation, hysteresis, stretch out, leakage current and interface state density D"i"t". By analyzing the CV data for films with different oxide thickness we find that the dielectric constant of La"2O"3 has a medium k-value of about 11.The same data indicate that there is no interfacial layer, which is confirmed by high resolution transmission electron microscopy (HRTEM) observations. These results suggest that a strong reaction with the Ge substrate may take place so that a La-Ge-O compound may form over the entire film thickness reducing the k-value. This reaction layer could be responsible for the reduction of Dit indicating good passivating properties. However, it may limit gate oxide scaling in future Ge MOS devices.