Effects of Carbon Incorporation on Electrical Characteristics and Thermal Stability of Ti/TiO2/n-Ge MIS Contact

The effects of carbon incorporation on the thermal stability of the interfacial TiO2 layer and the electrical characteristics of Ti/TiO2/n-Ge contacts were investigated. The improved thermal stability and contact characteristics of Ti/TiO2/n-Ge contacts were characterized in terms of Schottky barrier height (SBH) and specific contact resistivity (rho(c)) using the Schottky diode and circular transmission line model (CTLM). The values of SBH and rho(c) increased after the rapid thermal annealing (RTA) above 550 degrees C. The current density-bias voltage (J - V) curves of the Schottky diode showed a change of contact characteristics from Ohmic-like behavior to rectifying. This thermal instability was mainly caused by the decomposition of the interfacial TiO2 layer after high-temperature annealing. The structural degradation was confirmed by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) analyses. When carbon ions were incorporated into the interfacial TiO2 layer, the SBH and rho(c) values showed relatively stable characteristics as the RTA temperature increased up to 600 degrees C. The EELS mapping showed that the diffusion of oxygen from the interfacial TiO2 layer was effectively suppressed thanks to the incorporation of carbon. Thus, the carbon incorporation can improve the thermal stability of the interfacial TiO2 layer and the metal-insulator-semiconductor contact characteristics for Ge-based device applications.