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 (ρ_c) using the Schottky diode and circular transmission line model (CTLM). The values of SBH and ρ_c increased after the rapid thermal annealing (RTA) above 550 °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 ρ_c values showed relatively stable characteristics as the RTA temperature increased up to 600 °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.