Device operation of P‐ion‐implanted n‐BaSi2/p‐Si heterojunction solar cells

Abstract

AbstractWe formed phosphorous(P)‐ion‐implanted n‐BaSi2 films on p‐Si(111) substrates and demonstrated solar‐cell functionality of the n‐BaSi2/p‐Si heterojunction under AM1.5 illumination. The BaSi2 films were grown by molecular beam epitaxy, followed by implantation of P ions to the BaSi2 films using PF3 gas at an energy of 10 keV and a dose of 1 × 1014 cm−2. Subsequent postannealing was conducted at 500°C in Ar for different durations (t = 30–480 s) to activate the P atoms. The diffusion coefficient for P atoms in BaSi2 was evaluated from the depth profiles of P atoms by secondary‐ion mass spectrometry. The activation energies of lattice and grain boundary diffusion were found to be 1.1 ± 0.6 and 2.5 ± 0.6 eV, respectively. From the analysis of Raman and photoluminescence spectra, the ion implantation damage was recovered by the postannealing. For one treated sample with t = 120 s, the internal quantum efficiency reached 67% at a wavelength of 870 nm. This is the highest ever achieved for n‐BaSi2/p‐Si heterojunction solar cells. Ion implantation is thus applicable to BaSi2 films grown by any other method. This achievement thereby opens a new route for the formation of BaSi2 solar cells.