Temperature dependence ofthe barrier at the tetrahedral amorphous carbon-siliconinterface

Abstract

Tetrahedral amorphous carbon film (ta-C, rich insp3 bonds), 50 nm thick, was deposited by magnetronsputtering on n-type Si substrate at room temperature. Ohmiccontact to the ta-C film was formed by depositingstoichiometric titanium nitride (TiN) by magnetron sputtering oraluminum (Al) by electron-gun evaporation at room temperature.The capacitance-voltage characteristics at differenttemperatures show negligible hysteresis, indicating lowconcentration of mobile charges. Electrical conduction in theTiN (Al)/ta-C/n-Si structure, with the TiN or Al biasedpositively with respect to Si, was investigated in thetemperature range 80-300 K. Under high-field conditions, theelectrical conduction is consistent with thermally assistedFowler-Nordheim tunnelling of electrons from the Si substrateinto the ta-C film for temperatures for 80-260 K and trap-assistedband-to-band indirect tunnelling for higher temperatures. Underlow-field conditions, Poole-Frenkel emission dominates overtunnelling for temperatures even well below room temperature.The temperature dependence of the tunnelling current wasexplained in terms of the change in the effective barrierheight at the ta-C/n-Si interface.