Electric Field and Phosphorus Doping Roles on the Electronic and Optical Properties of SIC Nanocrystals: First Principles Study

We present a study of the electronic and optical properties of the hydrogen-terminated SIC nanocrystals (Si38C40H64, Si116C128H144 and Si242C252H232) using density functional theory calculations. The role of the nanocrystals size, external electric field induced to the nanocrystals and Phosphorus doping to the nanocrystals on the electronic and optical properties of the SIC nanocrystal have been investigated. We found that the energy gap of the nanocrystals varies slowly due to the size increasing i.e., 7.726, 7.372 and 7.053 eV for Si38C40H64, Si116C128H144 and Si242C252H232 nanocrystals, respectively. The induced electric field makes a noticeable red shift in the absorption peak particularly at field strength more than 1 V/nm. The carbon substitutional defects are appropriate for Phosphorus impurities as the formation energy of the Si242C252H232 nanocrystal as an example varies due to the different percentage of doping according to the -0.81, -0.64, -0.38 and -0.26 eV for 3%, 5%, 11% and 16% of doping, respectively.