Amorphous Carbon-Based Semiconductor Capable of Controlling Its Optical Gap and Conductivity by Incorporating Silicon and Nitrogen Atoms

Abstract

Optical gap-selective amorphous carbon (a-C) based n-type semiconductor materials were fabricated by incorporating silicon and nitrogen atoms by radio frequency plasma enhanced chemical vapor deposition method using a mixed solution of tetramethylsilane and 1,1,1,3,3,3-hexamethyldisilazane as a source material. The optical gaps can be controlled from 1.25 to 2.76 eV when Si/C ratio at amorphous Si-C network and sizes and number of sp2 clusters in multi-phase structure of the resulting carbon-rich amorphous silicon-carbon alloys (C-rich a-SiC) are varied by regulating Si atom%. The resulting Si 24 atom%-added C-rich a-SiC shows the optical gap of 1.76 eV, while Si 44 and 18 atom%-added C-rich a-SiC show 2.76 and 1.25 eV, respectively. The films show n-type conduction with the carrier density of ca. 1014 cm-3 and the carrier mobility of ca. 1 cm2V-1s-1 by doping N atoms of 1 atom%. The results of photocurrent measurement under UV exposure are verified and showed that the films have a function of photon-to-electron conversion with the quantum yield of ca. 7%, approximately one-third of the value obtained at anatase-type titanium oxide prepared by the sol-gel method. © 2016 The Electrochemical Society.