Drastic enhancement of photoresponsivity in C-doped BaSi2 films formed by radio-frequency sputtering

We formed carbon (C)-doped BaSi2 films by RF sputtering of BaSi2 and SiC targets simultaneously, and measured their optical properties. In the Raman spectra of BaSi2 films, peaks corresponding to vibrational modes of Si tetrahedra in the lattice of BaSi2 appear. On the other hand, in C-doped BaSi2 films, new peaks at around 260, 310, and 630 cm(-1) other than those of BaSi2 films were observed. As the RF power of the SiC target (PSiC) increased, these intensities increased. The absorption edge of C-doped BaSi2 films was shifted to higher energies from 1.19 to 1.30 eV with increasing PSiC. We achieved the highest photoresponsivity of 1 A W-1 ever achieved for BaSi2 films at a bias voltage of 0.1 V applied between the top and bottom electrodes. The marked enhancement of photoresponsivity was interpreted to originate from the increased carrier lifetime in Cdoped BaSi2 films. (c) 2020 The Japan Society of Applied Physics